1. Visualizing an Experiment That Manipulates Two Variables Click here to get started Click here to get started Quit © 2015 Mark Mitchell & Janina Jolley

2. Menu Introduction: Experiments look for differences between conditions to discover what made a differenceIntroduction: Experiments look for differences between conditions to discover what made a difference Using four experiments to manipulate the two treatments Using one experiment to do the job of four Isolating simple main effects by treating a factorial experiment like 4 separate simple experimentsIsolating simple main effects by treating a factorial experiment like 4 separate simple experiments Combining (averaging) a factor’s simple main effects to estimate overall main effectsCombining (averaging) a factor’s simple main effects to estimate overall main effects Comparing (subtracting) a factor’s simple main effects to look for interactionsComparing (subtracting) a factor’s simple main effects to look for interactions Making graphs of 2 X 2 factorial experiments Interpreting graphs of 2 X 2 factorial experiments Quiz Quit

3. Measuring “Readability” Imagine we have participants rate how easy it is to read the print on a page the way some people rate movies-- with a star (  ) system. In our system, one star (  ) means not very readable, whereas 5 stars (      ) means very readable. To get an idea of how this rating system might work, see the next slide.

4. Sample Text and Star Ratings Instructions: Rate the readability of the text below. Ratings Text ***** Text **** Text*** Text ** Text *

5. An Experimental Approach Now, let’s think about how we would see whether exposing different groups to different colors of text and different backgrounds will make a difference in how readable words are. For example, imagine the following four experiments.

6. Simple Experiment 1: What Would Be Manipulated? Alice investigates the effect of the darkness of the background on readability. To see whether background makes a difference, she would manipulate A. A. The color of the text B. B. The darkness of the background C. C. Nothing. Text

7. Simple Experiment 1: Thinking About Differences If Alice were to suggest a study in which she looked only at dark text against a dark background to see whether background makes a difference, A. that would be a perfectly good study.A. B. B. that would be a bad idea because, to determine whether background makes a difference, you have to look at the difference between groups getting different backgrounds—you can’t just look at a single group. Text * Alice’s proposed study

8. Simple Experiment 1: Thinking About Differences To see whether background makes a difference, Alice should look at A. A. The readability of text in the dark background. B. B. The readability of text in the light background. C. C. The difference between how readable the text was in the two backgrounds. Alice’s experiment Text

9. Simple Experiment 1: Results Alice finds a rating of ____ stars for the dark background and a rating of ___ stars for the light background. A. 1, 4 1, 4 B. 4, 1 4, 1 C. 2, 42, 4 D. 4, 24, 2 Background DarkLight (**) Rating(****) Rating

10. Simple Experiment 1: Conclusions Alice finds that text is easier to read when the background is A. Light B. Dark Background DarkLight (**) Rating(****) Rating

11. Simple Experiment 1: Effect Size Alice finds that a light background makes a difference of (has an effect of ) about ____ stars. A. One B. Two C. Three D. Four Background DarkLight (**) Rating(****) Rating

12. Simple Experiment 2: Manipulating the Background Bob investigates the effect of background on readability. Text Bob’s experiment

13. Simple Experiment 2: Results Bob finds that print is easier to read when the background is A. Light B. Dark Background DarkLight **** Rating* Rating

14. Simple Experiment 2: Effect Size In Bob’s study, our best guess would be that having a dark background seems to make a difference of about _____ stars. A. 1 (*) B. 2 (**) C. 3 (***) D. 4 (****) Background DarkLight **** Rating

15. Simple Experiment 3: What Is Manipulated? Carl investigates the effect of text color on readability. Carl’s experiment Black Text White Text

16. Simple Experiment 3: Results According to Carl’s experiment, which color of text is easier to read? A.BlackBlack B.WhiteWhite C.NeitherNeither Text color ** Rating **** Rating

17. Simple Experiment 4: What Is Manipulated? Dana investigates the effect of text color on readability. Dana’s experiment Black Text White Text

18. Simple Experiment 4: Results According to Dana’s simple experiment, which color of text is easier to read? A.BlackBlack B.WhiteWhite C.NeitherNeither Text color **** Rating * Rating

19. 4 Studies--4 Different Results We just looked at four studies that obtained four different results. Some of these results seem to conflict (e.g., in one study, black text was more readable than white text; in another, black text was less readable than white text).

20. 4 Studies--4 Different Results We just looked at four studies that obtained four different results. Some of these results seem to conflict (e.g., in one study, black text was more readable than white text; in another, black text was less readable than white text). To reduce this confusion, we could do a study that combines all four experiments into one.

21. Text Below is a table of a 4-group experiment that contains all the groups that were in 4 separate simple experiments. Note that each group gets a different combination of text color and background color (e.g., Group 1 gets black text against a dark background, Group 2 gets black text against a light background, Group 3 gets white text against a dark background, and Group 4 gets white text against a light background).

22. Because there are 2 levels of the text color factor (black and white) and 2 levels of the background factor (dark and light), this is a 2 by 2 factorial experiment. Text

23. Here are the results of that 2 X 2 factorial experiment: Background Dark Readability = ** Readability = ****

24. Understanding simple main effects A 2 X 2 experiment contains 4 simple experiments. –Specifically, each of its 2 rows contains a simple experiment and each of its 2 columns contains a simple experiment.

25. Understanding simple main effects A 2 X 2 experiment contains 4 simple experiments. –Specifically, the 2 rows each contain a simple experiment and the 2 columns each contain a simple experiment. So, by treating each row and each column in a 2 X 2 experiment as a separate simple experiment, you could find the same effects that you could find by doing 4 separate simple experiments. These effects are called simple main effects.

26. Can you see the four simple experiments inside this 2 X 2 experiment? Click on each of the numbered arrows to get a better view. When you are done, answer the question at the bottom of this slide. Background brightness DarkLight Text color Black White White 3 1 2 4 Each of the effects you get from the four simple experiments inside the bigger experiment are called: A. Simple main effects, B. Overall main effects, C. InteractionsSimple main effectsOverall main effectsInteractions

27. As you saw, each of those 4 simple experiments produces a simple main effect, making a total of 4 simple main effects. Note that you do not find these effects by looking at individual cells. Instead, you find them by looking at differences between cells. That is, you find out whether something had an effect by seeing whether it made a difference. Background brightness DarkLight Text color Black White White 3 1 2 4

28. Let’s take a closer look at those 4 simple main effects. Background color DarkLight Text colorBlack Black Black White

29. Let’s start with the simple main effect we can see by looking at the first row. When we look at the first row, what varies (differs)? That is, the first row is like a simple experiment that varies A. Text color (black vs. white) B. Background (dark vs. light) A. Text color B. Background Background Dark Text color ** ****

30. So, when we look at the top row, what are we comparing? A. The dark background with the light background—for black text. B. The dark background with the light background—for white text. C. The black text with the white text. A. The dark background with the light background—for black text. B. The dark background with the light background—for white text. C. The black text with the white text. Background DarkLight Text color ** **** White **** *

31. What does moving from dark to light background do to readability of black text? A. Increases readability. B. Decreases readability. A. Increases readability B. Decreases readability Background DarkLight Text color ** **** White <<

32. What, specifically, does moving from dark to light background do to readability of black text? A. Increases readability by one star. B. Increases readability by two stars (from ** to ****). A. Increases readability by one star. B. Increases readability by two stars Background DarkLight Text color ** **** White

33. What simple main effect can we detect in the first row? A. Text color: Black print differs from white print: Black print is easier to see than white print. B. Background: With black text, light backgrounds are better than dark backgrounds. A. Text color: B. Background: Background brightness Dark Text color ** **** <<

34. What effect can we detect by looking at a single cell (a single group mean) by itself, such as the dark background, black print cell? A. The simple main effect of text color B. The simple main effect of background C. Nothing—You can only detect effects (differences that treatments make) by looking at differences between cells. A. B. C. Background brightness Dark Text color ** ****

35. Now, let’s look at the second (bottom) row. Background brightness Dark Text color ** **** >>>

36. What varies (differs) across the second row? That is, the second row is like a simple experiment that varies A. Text color (black vs. white) B. Background darkness (dark vs. light) A. Text color B. Background darkness Background Dark Text color ****

37. What simple main effect can we detect in the “White text” row? A. Text color: White print is easier to see than black print. B. Background: With white text, dark backgrounds are better than light backgrounds. A. Text color: B. Background: Background brightness Dark Text color **** >>>

38. What is our best guess for the simple main effect of background in the white text conditions? A. One star B. Two stars C. Three stars D. Four stars A. One star B. Two stars C. Three stars D. Four stars Background brightness Dark Text color **** >>>

39. Now, let’s look at the first column. Background brightness Dark Text color ** Black text **** White text

40. What would we call the first column? A. The dark background column B. The light background column C. The black text column A. The dark background column B. The light background column C. The black text column < Background brightness Dark Text color ** **** *

41. What changes as we go down the dark background column? That is, the dark background column is like a simple experiment that varies A. Text color (black vs. white) B. Background brightness (dark vs. light) A. Text color B. Background brightness < Background brightness Dark Text color ** **** *

42. Which effect can we detect in the first column? A. Text color: In the dark background condition, white print is easier to see than black print. B. Text color: In the dark background condition, black print is easier to see than white print. C. Background: Dark backgrounds are better than light backgrounds. A. Text color: B. Text color C. Background: Background brightness Dark Text color ** **** *

43. In the dark background conditions, what is our best estimate of the text color simple main effect? A. One star. B. Two stars. C. Three stars. D. Four stars. A. One star. B. Two stars. C. Three stars. D. Four stars. Background brightness Dark Text color ** **** *

44. Now, let’s look at the second column. Background brightness DarkLight Text color ** **** *

45. What differs (varies) as we go down the light background column? That is, the light background column is like a simple experiment that varies A. Text color B. Background A. Text color B. Background Background brightness DarkLight Text color ** ****

46. What effect can we detect in the light background column? A. Text color: In the light background conditions, black print is easier to read than white print B. Background: Light backgrounds are better than dark backgrounds. A. Text color: B. Background: Background brightness DarkLight Text color ** ****

47. In the light background conditions, what is our best estimate of the text color simple main effect? A. One star. B. Two stars. C. Three stars. D. Four stars. A. One star. B. Two stars. C. Three stars. D. Four stars. Background brightness DarkLight Text color ** ****

48. Our one experiment has produced 4 simple main effects. Can these 4 simple main effects also be looked at as 2 pairs of main effects: a pair of main effects for each factor? A.YesYes B.NoNo

49. Yes, we have a pair of simple main effects for each factor. In our example, we have 2 simple main effects for white text vs. black text 1.White text vs. black text on light backgrounds and 2.White text vs. black text on dark backgrounds 2 simple main effects for dark vs. light background 1. Light background vs. dark background for white text, and 2. Light background vs. dark background for black text. In the 2 X 2, do we have 2 pairs of simple main effects?

50. Can we combine and compare each factor’s pair of simple main effects? A.Yes, because the data come from the same experiment.Yes B. No. No.

51. Right! We can look at pairs of main effects. Specifically, we can pair up the 2 simple main effects and the 2 column simple main effects. But before we pair up our main effects, let’s review. The top row can be used to determine: A. The simple main effect of background for the black text conditions. B. The simple main effect of black text. A. The simple main effect of background for the black text conditions. B. The simple main effect of black text. Background Dark Text color ** **** White > <<

52. Background Dark Text color ** **** = >>> The bottom row can be used to determine: A.The simple main effect for background for the white text conditions: This effect is four stars.The simple main effect for background for the white text conditions: This effect is four stars. B. The simple main effect of background for the white text conditions: This effect is three stars.The simple main effect of background for the white text conditions: This effect is three stars. C.The simple main effect of white text: This effect is four stars.The simple main effect of white text: This effect is four stars.

53. Background Dark Text color ** **** So, the two simple main effects we found by comparing cells within rows represent A. A. The effects of the background on the readability of black text (a 2 star edge to light backgrounds) and the effects of background on the readability of white text (a 3 star edge to dark backgrounds). B. B. The effect of text color << >>>

54. Combining a Factor’s Pair of Simple Main Effects to Get That Factor’s Overall Main Effect You now know how to estimate a factor’s simple main effects. To find the average effect that a factor has in a study, average its simple main effects. This average effect is called the factor’s overall main effect. Main Menu

55. Combining (averaging) the two simple main effects that we found by comparing cells within the black and white rows would give us A. A. The overall main effect of background, combined across both black and white text. B. B. The effect of text color. C. C. The background by text interaction. Background Dark Text color ** << >>>

56. From averaging/combining the two row simple main effects, you would conclude that A. A. Dark backgrounds are, on average, slightly more readable than light backgrounds. B. B. Light backgrounds are, on average, more readable than dark backgrounds. C. C. White text is more readable than black text. Background Dark Text color ** Totals << >>> >

57. Before we start combining our two simple column main effects, let’s look at each individual column. First, let’s look at the dark background column. For that column, how much more effective is white print than black print? A. One star B. Two stars C. Three stars D. Four starsOne starTwo starsThree starsFour stars Background DarkLight Text color ** Black **** White >

58. Now, let’s look at the light background column. For that column, how much more visible is black text than white text? A. One star B. Two stars C. Three stars D. Four stars A. One star B. Two stars C. Three stars D. Four stars Background DarkLight Text color Black **** White =

59. Background DarkLight Text color ** **** **** ** *** Averaging/combining the two simple main effects we found by comparing cells within the two background columns would give us A. A. The main (average) effects of varying background B. B. The main (average) effect of varying text color C. C. The background by text interaction

60. The main effect of varying text color from black to white is, on average, to A. A. Have no effect B. B. Decrease readability (black text is more readable) C. C. Increase readability (white text is more readable) Background DarkLight Text color ** **** **** ** *** *

61. Summary: Overall Main Effects You know that the average of a factor’s simple main effects gives you the overall main effect of that factor. But how do you tell whether there is an interaction?

62. First, let’s be sure we know what we mean by an interaction. An interaction means that the effect of one factor depends on the level of another factor. That is, with an interaction, we cannot say what the effect of varying one factor will be unless we also know the level of the other factor. In other words, if we have an interaction, a factor’s simple main effects will differ. For example, the difference in readability when we change from black text to white text would be – negative when we had a light background, but –positive when we had a dark background. Defining interactions See more examples of interactions dark background light background With interactions, combinations of variables may have effects that are more than the sum of their individual effects. Combining variables may result in effects that are much greater than the sum of the individual effects (think Mentos and diet Coke) less than or even opposite of the sum of the individual effects (e.g., you might generally like turkey and smore-flavored pop tarts, but not like putting them together into a turkey pop tart sandwich.).Mentos and diet Coke

63. Understanding interactions If there is an interaction, a factor’s simple main effects differ from each other. True False Background DarkLight Background simple main effects Text color ****+2 Example of an interaction

64. Understanding interactions If there is an interaction, a factor’s simple main effects differ from the factor’s overall main effect. TrueFalse Background DarkLight Background simple main effects Overall background main effect Text color ****+2 0 Example of an interaction

65. Detecting interactions You determine whether you have an interaction by comparing a factor’s pair of simple main effects. –If a factor’s simple main effects differ significantly from each other, there is an interaction. Warning 1: Only compare simple main effects from the same factor. Warning 2: If the overall main effects of two different factors differ, that does not mean anything about whether there is an interaction.

66. In which case, would there be an interaction? The effect of changing text from black to white was different in the dark background condition than in the light background. No, not necessarily. If we have a main effect of background such that light backgrounds are better than dark backgrounds and a main effect for black text being better than white text, those main effects would normally cause black text to be most visible on light backgrounds. A B C The most visible condition was the black text on a light background condition. Both A and B.

67. Which experiment found an interaction? Experiment A Background DarkLight Text color ** **** **** Experiment B Background DarkLight Text color * *** ** A. A. Experiment A B. B. Experiment B C. C. Both Experiments A and B

68. Background DarkLight Text color ** ** **** ** *** Do the two black/white simple main effects differ? A. Yes B. No

69. Background DarkLight Text color ** ** **** ** *** Is there an interaction between text color and background? YesNo Is the effect of going from black text to white text different in the dark background condition than in the light background condition?

70. Background DarkLight Text color ** **** **** We could also uncover the interaction by comparing the pair of row main effects. Recall that the two row simple main effects represent A. A. The effects of background on the readability of black text and the effects of background on the readability of white text. B. B. The effect of text color (black versus white). << >>>

71. Background DarkLight Text color ** **** **** Do the two row effects (the effects of background) differ? A. A. Yes B. B. No << >>>

72. Background DarkLight Text color ** **** **** Is there an interaction? A. A. Yes B. B. No << >>>

73. Background DarkLight Text color ** **** **** To review, looking at the difference between background’s two simple main effects would tell us that there was a(n) << >>> A. Background main effect: A. Background main effect: On average, the background has an effect. B. Text color main effect: B. Text color main effect: On average, text color has an effect. C. Background by text color interaction: C. Background by text color interaction: Background has one effect for black text, but a different effect for white text.

74. Averaging the two simple main effects for background would tell us whether there was a(n) A.Text color main effect: On average, text color has an effect.Text color main effect: B.Background main effect: On average, the background has an effect.Background main effect: On average, the background has an effect. C.Text by background interaction: Background has one effect for black text, but a different effect for white text.Text by background interaction: Background has one effect for black text, but a different effect for white text.

75. Background DarkLight Text color ** **** **** Finding a difference between two cells in the black text row suggests a << A.text main effect.text main effect. B.background main effect.background main effect C.simple main effect of background in the black text condition.simple main effect of background in the black text condition. D.simple main effect of black text.simple main effect of black text. E.text by background interaction.text by background interaction.

76. Background DarkLight Text color ** ** **** Finding that the difference between the two cells in one row is different from the difference between the two cells in another row suggests << >>> A.a main effect for the row variablea main effect for the row variable B.a main effect for the column variablea main effect for the column variable C.a simple main effect of the column variable in that row (e.g., an effect of background in the black text condition)a simple main effect of the column variable in that row (e.g., an effect of background in the black text condition) D. an interactionan interaction E.nothingnothing

77. Background DarkLight Text color ** Totals Finding that the average scores of the dark background column differ from average scores of the light background column suggests > A.a main effect for text colora main effect for text color B.a main effect for background darknessa main effect for background darkness C.an interactionan interaction Hint: What is the difference between the 2 columns?

78. Background DarkLightTotalsAverages Text color **** Finding that there is a difference between the average scores of two rows suggests (Hint: What is the difference between the two rows?) A.a main effect for the row variable (e.g., text color)a main effect for the row variable B.a main effect for the column variable (e.g., background)a main effect for the column variable C.an interactionan interaction

79. Now, let’s look at a different set of results. In the experiment below, when the background is dark, does varying the text color matter? A. Yes B. No Background color DarkLight Text color Black Black Black White White White Difference (Effect of varying color) = *** *

80. When the background is light, does varying the text color matter? A. Yes B. No Background DarkLight Text color Black Black Black White White White Difference (Effect of varying color) = ** *** *

81. When the background is light, what is our best guess about the effect of varying the text color? A. 1 star (*) B. 2 stars (**) C. 3 stars (***) Background DarkLight Text color Black Black Black White White White Difference = ** *** *

82. On the average, in this experiment, is black text more readable than white? A. A. Yes—there seems to be a text main effect. B. B. No—there does not seem to be a text main effect. Background color DarkLight Text color Black Black Black White White White Black/white difference *** * **

83. Does the effect of text color (black being more visible than white) differ depending on the background? A. Yes A. Yes —There is a text by background interaction. B. No B. No —There is not a text by background interaction. Background color DarkLight Text color Black Black Black White White White Black/white difference *** * **

84. When the text color is black, does varying the background matter? A. Yes B. No Background DarkLight Text color Black Black Black White White White *** *

85. When the text color is white, does varying the background matter? A. Yes B. No Background DarkLight Text color Black Black Black White White White *** *

86. = > On the average, in this experiment, is a dark background better than a light background? Background color DarkLight Text color Black Black Black White White White Totals Averages *** * * Yes No*

87. The “Differences” Column could also be labeled A. A. Differences between dark and light backgrounds. B. B. Effects of varying the background. CC. Both A and B. Background DarkLightDifferences Text color Black Black Black White White White *** * **

88. There is a difference in readability (number of stars) between the dark and the light background in the black text condition. A. TrueB. False Background DarkLightDifferences Text color Black Black White White White *** * **

89. There seems to be a simple main effect of background in the black text condition. A. TrueB. False Background DarkLight Text color Black Black White White White *** *

90. There is a difference in readability between the dark and the light background in the white text condition. A. TrueB. False Background DarkLightDifferences Text color Black Black Black White White White *** * **

91. The difference in readability (number of stars) between the dark background and the light background in the white text condition is A. 0 starsB. 1 starA. 0 starsB. 1 star C. 2 stars D. 3 starsC. 2 stars D. 3 stars Background DarkLight Text color Black Black Black White White White *** *

92. There seems to be a simple main effect of background in the white text condition. A. TrueB. False Background DarkLight Text color Black Black Black White White White *** *

93. Overall (averaged over both text colors), there seems to be a main effect of background. A. TrueB. False Background DarkLightDifferences Text color Black Black Black White White White Total= Average = /2 = >> =

94. In this experiment, on average, is black text more readable than white? A.Yes—there seems to be a text main effect.Yes B.No—there does not seem to be a text main effect.No Background DarkLight Text color Black Black Black White White White Black - White *** *

95. What 3 things do we find from looking at this study? Background color BlackWhite Text colorBlackBlack ***Black **** WhiteWhite ***White *

96. 1. On average, black text is easier to read than white text. In other words… Background color BlackWhite Text colorBlackBlack ***Black **** WhiteWhite ***White *

97. 1. There is a main effect for text color. Background color BlackWhite Text colorBlackBlack ***Black **** White White ***White * Black - White ***

98. 2. Over all, the dark background is more effective than the light background. In other words,… Background BlackWhite Text colorBlackBlack *** Black **** WhiteWhite *** White * Background totals *** ** >>

99. 2. There is an main effect for background. Background brightness Dark Light Text colorBlack White ******* ****

100. 3. But the effect of the text color depends on the background color. In other words, … Background brightness BlackWhite Text colorBlackBlack ***Black **** WhiteWhite ***White * < >>

101. 3. There is a background by text interaction. Background DarkLight Text colorBlackBlack *** Black **** WhiteWhite *** White * >> <

102. Review of the terms 1.Black text, on average, is better than white text. This would be called A.An overall main effect for text.An overall main effect for text. B.An overall main effect for background.An overall main effect for background C.A text by background interaction.A text by background interaction.

103. Review of the terms 2. Dark background, on average, is better than light background. This would be called A.An overall main effect for text.An overall main effect for text. B.An overall main effect for background.An overall main effect for background. C.A text by background interaction.A text by background interaction.

104. Review of the terms 3. Depending on the background, black text may be more effective than white text. This would be called A.An overall main effect for text.An overall main effect for text. B.An overall main effect for background.An overall main effect for background. C.A text by background interaction.A text by background interaction.

105. 1. A simple experiment In the black text conditions, the light background is better than the dark background. Background Dark Text color** Click this button to return to the table <<

106. 2. A simple experiment In the white text conditions, the dark background is better than the light background. Background DarkLight Text color **** Click this button to return to the table >>>

107. 3. A simple experiment With a dark background, white text is easier to read than black text. Click this button to return to the table. Background Dark Text color ** ** **

108. 4. A simple experiment With a light background, black text is easier to read than white text. Click this button to return to the table Background Text color **** * ***

109. From Table to Graph To understand the results of factorial experiments, you will often need to interpret a graph of those results. In this section, we will help you do that. We will start by helping you see how to turn a table into a graph. Main Menu

110. Black text Dark background Light background Black Text Black White Text White *** ■ **** ■ *** * ■ White text * From table to graph: Click the top row of the table to see that row converted into a line on a graph. Then, click on the second row to see it graphed. * ***

111. Background DarkLight Text color Black ** **** White *** Plot the points by clicking on the four individual cells (where it says “Plot me”). ***** *** ◊ ◊ * Dark Light Background White text Black text ■ ■**** ** *** Plot me ***

112. Interpreting Graphs Now that you have seen how to turn a table of means of a 2 X 2 factorial experiment into a graph, let’s practice interpreting these graphs. You will start by determining whether the graphs indicate an interaction. If the lines are parallel, there is not an interaction. If the lines are not parallel, there may be an interaction (we would have to do a statistical significance test to be sure). Quit

113. If two lines are parallel, they have the same slope. That is, they are changing in the same way. True False Two parallel lines are so much alike. Too bad they will never met.

114. Does this graph suggest an interaction between text and background? ***** ** * Dark Light Background Black text White text Yes No Are the lines changing differently, like they would if there was an interaction?

115. ***** **** *** * Red text Blue text Does this graph suggest an interaction between text and background? Dark Light Background Yes Are the lines changing in different ways, like they would if there was an interaction? No

116. ***** **** *** * Red text Blue text Does this graph suggest an interaction between text and background? A.YesYes B.NoNo Dark Light Background

117. ***** **** *** ** * Red text Blue text Does this graph suggest an interaction between text and background? A.YesYes B.NoNo Dark Light Background Remember, if the lines are not parallel, there may be an interaction.

118. ***** **** *** ** Red text Blue text Does this graph suggest an interaction between text and background? A.YesYes B.NoNo Dark Light Background

119. ***** **** *** * Red text Blue text If one line is, on average, higher than another, that difference in average height suggests a main effect for the line variable. In this case, text color is the line variable. These results suggest that blue text is more readable than red text. Dark Light Background

120. ***** **** *** * Red text Blue text One way to tell whether one line is higher than the other –that is to see whether there may be an effect for the line variable—is to see whether the midpoints of the two lines differ. Dark Light Background  

121. ***** **** *** * Red text Blue text If the midpoints of the lines are different, that suggests A.A main effect for the line variable (e.g., text color)A main effect for the line variable (e.g., text color) B.A main effect for the variable labeled on the bottom of the graph (in this example, background darkness)A main effect for the variable labeled on the bottom of the graph (in this example, background darkness) C. An interactionAn interaction Dark Light Background  

122. ***** **** *** ** * Dark Light Background This graph suggests no main effects or interactions. TrueFalse TrueFalse Black text line White text line * *

123. ***** ** * Dark Light Background Does the graph below suggest a main effect of text color? Black text Yellow text * * Is the midpoint of the black text line above the midpoint of the yellow text line—and does that suggest that line color matters? No Yes

124. ***** **** *** ** Red text Blue text According to the graph below, is there a main effect for text color? Dark Light Background   Are the midpoints of the red and blue lines significantly different? Yes No

125. ***** **** *** * Red text Blue text If the points on the left side of the graph are, on average, higher—or lower— than the points on the right side, that difference in average height suggests a main effect for factor labeled at the bottom of the graph. Thus, in this case, the graph suggests that darkness of background matters. Specifically, according to the graph below, light backgrounds are better than dark backgrounds. Dark Light Background

126. ***** **** *** * Red text Blue text In this case, is there is a main effect for background? Dark Light Background  Yes Is the average height of the lines different (i.e., higher or lower) on the dark background side of the graph than on the light background side? No

127. Does the graph below suggest a main effect of background? Black text Yellow text ***** ** * * Dark Light Background No! If you average the two lines, you would get a flat line: A line whose height does not change as it goes from left (the dark background side of the graph) to right (the light background side of the graph). No Yes

128. ***** **** *** * Red text Blue text If one line is, on average, higher than another and both lines are sloping up, you may have a main effect for the line variable (in this case, text color) and the variable on the x-axis (in this case, darkness of background). A.TrueTrue B.FalseFalse Dark Light Background

129. ***** **** *** * Red text Blue text If the lines are parallel, this means they are changing at the same rate as they go from one side of the graph to the other. In this case, it means that, as we go from the dark background to the light background side of the graph, scores in the red text condition change to the same degree as scores in the blue text condition. Consequently, the difference between red text and blue text is a 1 star superiority for red text in both the dark and light background conditions. Because text color’s effect is the same in both background conditions, there is no interaction between text color and background. A.TrueTrue B. FalseFalse Dark Light Background * *

130. ***** **** *** * Red text Blue text If one line is, on average, higher than another and both lines are sloping down, you may have two main effects: one for the line variable (in this case, text color) and one for the variable that varies as you go from left to right (in this case, background). A.TrueTrue B.FalseFalse Dark Light Background

131. ***** **** *** * Red text Blue text The graph below suggests that there are two main effects. However, because the lines are parallel, there is no interaction. A.TrueTrue B. False False Dark Light Background

132. ***** **** *** * Red text Blue text As you can see, with a black background, red text is more readable than blue text. However, with a green background, blue text is just as readable as red text. Given those facts, it appears we have an interaction. A.YesYes B.NoNo Black Green Background Are the lines are going in different directions, as they would with an interaction? Does the effect of changing background from black to green depend on whether we are talking about red text or blue text? Click if you want a hint

133. ***** **** *** * Red text Blue text As you can see, with a black background, red text is more readable than blue text. However, with a green background, blue text is just as readable as red text. Given those facts, it appears we have both an interaction and a main effect for text color. Black Green Background Yes No Is the red line above the blue line, indicating an effect for text color? Is the superiority of red text over blue text greater in the black background condition than in the green background condition?

134. ***** **** *** * Red text Blue text From the graph, it appears we have a main effect for background. Black Green Background Yes Is the average height of the lines when they are on the black background side of the graph different from the average height of those lines when they are on the green background side? No

135. ***** **** *** * White text Yellow text Does this graph suggests an interaction between text color and background color? Black Green Background No Is yellow text affected differently by the shift to a green background than white text? Yes

136. ***** **** *** * White text Yellow text Does this graph suggests a main effect for text color ? Black Green Background Yes No Is the white text line above the yellow text line?

137. ***** **** *** * White text Yellow text Does this graph suggest a main effect for background? Black Green Background No On average, are the lines higher on the left (black background) side of the graph than on the right (green background) side? Yes  

138. ***** **** *** * Blue text Yellow text Does this graph suggest an interaction between text color and background color? White Black Background No According to the graph, if we want to know if blue text is more readable than yellow text, do we have to say that it depends on the background? Yes

139. ***** **** *** * Blue text Yellow text Does this graph suggest a main effect for text color? White Black Background Is the midpoint of the yellow text line clearly higher than the midpoint of blue text line? Yes No

140. ***** **** *** * Black text White text In this case, do we have a text color main effect? BlueRed Background Yes No Is the white text line higher black text line?

141. ***** **** *** * Black text White text In this case, we have a background color main effect. BlueRed Background Yes No Are the lines, on the average, higher on the red side of the graph than on the blue side?

142. ***** **** *** * Black text White text In this case, we have an interaction between background color and text color. BlueRed Background Yes No Is the benefit of red background specific to the black text condition?

143. Click on the two points you would have to compare to see the simple main effect of text in the dark background conditions. ***** **** *** ** * Dark Light Background Black text White text * * No Yes * *

144. ***** **** *** * Black text White text What would we look at to see whether there was main effect for text color? BlueRed Background Whether the slopes of the two lines differ Whether the slopes of the two lines differ Whether the lines are, on average, at different heights Whether the lines are, on average, at different heights Whether the lines are higher, on average, on one side of the graph than the other Whether the lines are higher, on average, on one side of the graph than the other

145. ***** **** *** * Black text White text What would we look at to see whether there was an interaction between text color and background color? BlueRed Background Whether the slopes of the two lines differ Whether the slopes of the two lines differ Whether the lines are, on average, at different heights Whether the lines are, on average, at different heights Whether the lines are higher, on average, on one side of the graph than the other Whether the lines are higher, on average, on one side of the graph than the other

146. ***** **** *** * Black text White text What would we look at to see whether there was a main effect for background color? BlueRed Background Whether the slopes of the two lines differ Whether the slopes of the two lines differ Whether the lines are, on average, at different heights Whether the lines are, on average, at different heights Whether the lines are higher, on average, on one side of the graph than the other Whether the lines are higher, on average, on one side of the graph than the other

147. Now, imagine an experiment in which 1. The text color is varied between blue and green, and 2. The thickness of the lines making up the letters is varied between thin (regular text) and thick (bold). Imagine that the outcome (dependent) variable is readability, rated on a 1 (poor) to 5 (excellent) scale. The results of that study are on the next slide. Click on the buttons on the next slide to see the results of that study.

148. 3 6 3 6 Normal (Thin lines) Bold (Thick lines) Font style Blue Green Text Color Simple main effect for text color in the normal ( thin line) conditions * * +3 Simple main effect for text color in the bold (thick line) conditions Simple main effect for font style in the green line condition Simple main effect for font style in the blue line condition 0 0 +3 Click on the 4 buttons to see the 4 simple main effects.

149. 3 6 3 6 Normal (Thin lines) Bold (Thick lines) Font type Blue Green Text Color Is there a main effect for line color? Is there a main effect for line color? Is there a main effect for line thickness? Is there a main effect for line thickness? Is there an interaction between line color and line type? Is there an interaction between line color and line type? Yes, the blue line is above the green line. Note that the midpoint of the blue line is higher than the midpoint of the green line. No, the thin line side of the graph is just as high as the thick line side of the graph. No, the green and blue lines are parallel, showing that they are changing at the same rate. * * ** Click on the 3 blue buttons to see what effects this graph reveals.

150. 3 6 7 NormalBold Font type Blue Green Text Color Yes Yes, the blue line is above the green line. 4 No Does there seem to be a color main effect?

151. 3 6 7 Normal Bold Font type Blue Green Text Color Yes Yes, the normal font side of the graph is lower than the bold font side of the graph. 4 Does there seem to be a main effect for font? No

152. 3 6 7 Normal Bold Font type Blue Green Text Color Yes No, the lines are parallel, showing that they are changing at the same rate. That is, both the green line and the blue line go up one unit as they go from normal to bold. 4 Does there seem to be an interaction between color font? No

153. 3 4 3 4 Thin Thick Line Thickness Blue Green Text Color In the experiment tabled below, does color seem to have an effect? On average, is the blue text line higher than the green text line? Yes No

154. 3 4 3 4 Thin Thick Line Thickness Blue Green Text Color In the experiment below, does line thickness seem to have an effect? Is the average height of the lines different (i.e., higher or lower) on the thin side than on the thick side? Yes No

155. 4 6 4 6 Normal text Bold text Font Blue Green Text Color Comparing the midpoint of the blue line (marked with a blue asterisk) with the midpoint of the green line (marked with a green asterisk),you can see that there seems to be A.A main effect for text colorA main effect for text color B.A main effect for fontA main effect for font C.An interaction between text color and fontAn interaction between text color and font * *

156. 4 6 4 6 Thin lines Thick lines Line type Blue Green Text Color We put one box at the midpoint between the means for the thin line groups and another box at the midpoint between the means for the thick lines. If you drew a line between those points, the line would A.Slope up, indicating a main effect for line thicknessSlope up, indicating a main effect for line thickness B.Slope up, indicating a main effect for colorSlope up, indicating a main effect for color C. Go neither up nor down, suggesting no effect for line thickness

157. 2 3 4 5 Thin Thick Line Thickness Blue Green Text Color In the experiment tabled below, what is the simple main effect of line thickness in the blue text conditions? +2 12435

158. 2 3 4 5 Thin Thick Line Thickness Blue Green Text Color In the experiment tabled below, what is the simple main effect of line thickness in the green text conditions? 12435 +2

159. 2 3 4 5 Thin Thick Line Thickness Blue Green Text Color What is the simple main effect of color (blue vs. green) in the thin line conditions? 1435 +1 2

160. 2 3 4 5 Thin Thick Line Thickness Blue Green Text Color What is the simple main effect of color (blue vs. green) in the thick line conditions? +1 14352

161. 2 3 4 5 Thin Thick Line Thickness Blue Green Text Color What is the overall (average) main effect of color (blue vs. green) across all conditions? A.11 B.22 C.33 D.44 E.55

162. 2 3 4 5 Thin Thick Line Thickness Blue Green Text Color What is the overall, average main effect of line thickness across all conditions? A.11 B.22 C.33 D.44 E.55

163. 2 3 4 5 Thin Thick Line Thickness Blue Green Text Color Is the simple main effect of line thickness in the blue conditions different from the simple main effect of line thickness in the green conditions? A. Yes Yes B.NoNo

164. 2 3 4 5 Thin Thick Line thickness Blue Green Text Color Was there an interaction involving line thickness and text color? A. Yes Yes B.NoNo +2

165. A. Yes Yes B.No –and there is no interactionNo –and there is no interaction C.No, and there is an interactionNo, and there is an interaction 2 3 4 5 Normal Bold Font type Blue Green Text Color Was the main effect for line thickness (normal vs. bold) the same as the main effect for text color (green vs. blue)?

166. 3 4 4 3 Thin Thick Line Thickness Blue Green Text Color For the results graphed below, what is the simple main effect for going from thin to thick lines in the green text conditions? A.+1+1 B.00 C.-1

167. 3 4 4 3 Thin Thick Line Thickness Blue Green Text Color For the results graphed below, what is the simple main effect for going from thin to thick lines in the blue text conditions? A.+1+1 B.00 C.-1

168. 3 4 4 3 Thin (Normal) Thick (Bold) Line Thickness (Normal vs. Bold Text) Blue Green Text Color Is there a text color by line thickness interaction? There is an interaction, because the effect of text type is different depending on text color. In the green conditions, bold text is 1 point more readable than normal text. In the blue conditions, bold text is 1 point less readable than normal text. Yes No

169. 3 4 4 3 Thin Thick Line Thickness Blue Green Text Color Is there an overall main effect for text color? Yes No Correct. The midpoints of the blue and green lines are not different.

170. 3 4 4 3 Thin Thick Line Thickness Blue Green Text Color Is there an overall main effect line thickness? Yes No Correct. The average height of the thin and thick lines are not different.

171. Quiz Click on the green arrow button to go to the quiz. Quiz Quit

172. 2 4 3 5 Thin Thick Line Thickness Blue Green Text Color To determine the simple main effect of line thickness in the blue condition, you would A. Take the difference between 5 and 4. Take the difference between 5 and 4. B.Take the difference between 3 and 2Take the difference between 3 and 2 C.Take the difference between 4 and 2.Take the difference between 4 and 2. D.Take the difference between 5 and 3.Take the difference between 5 and 3. E.Take the difference between 5 and 4 and 3 and 2, then average those differences.Take the difference between 5 and 4 and 3 and 2, then average those differences. F.Take the difference between 5 and 4 and 3 and 2, then subtract those differences.Take the difference between 5 and 4 and 3 and 2, then subtract those differences.

173. 2 4 3 5 Thin Thick Line Thickness Blue Green Text Color To determine the simple main effect of line thickness in the green condition, you would A. Take the difference between 5 and 4. Take the difference between 5 and 4. B.Take the difference between 3 and 2Take the difference between 3 and 2 C.Take the difference between 4 and 2.Take the difference between 4 and 2. D.Take the difference between 5 and 3.Take the difference between 5 and 3. E.Take the difference between 5 and 4 and 3 and 2, then average those differences.Take the difference between 5 and 4 and 3 and 2, then average those differences. F.Take the difference between 5 and 4 and 3 and 2, then subtract those differences.Take the difference between 5 and 4 and 3 and 2, then subtract those differences.

174. 2 4 3 5 Thin Thick Line Thickness Blue Green Text Color To determine the overall main effect of line thickness, you would A. Take the difference between 5 and 4. Take the difference between 5 and 4. B.Take the difference between 3 and 2Take the difference between 3 and 2 C.Take the difference between 4 and 2 and the difference between 5 and 3, then average those differences.Take the difference between 4 and 2 and the difference between 5 and 3, then average those differences. D.Take the difference between 5 and 4 and the difference between 3 and 2, then average those differences.Take the difference between 5 and 4 and the difference between 3 and 2, then average those differences. E.Take the difference between 5 and 4 and 3 and 2, then subtract those differences.Take the difference between 5 and 4 and 3 and 2, then subtract those differences.

175. 2 4 3 5 Thin Thick Line Thickness Blue Green Text Color To find the interaction between line thickness and color, A. Take the difference between 5 and 4. Take the difference between 5 and 4. B.Take the difference between 3 and 2Take the difference between 3 and 2 C.Take the difference between 5 and 3.Take the difference between 5 and 3. D.Take the difference between 5 and 4 and 3 and 2, then average those differences. If that average is significantly greater than zero, there is an interaction.Take the difference between 5 and 4 and 3 and 2, then average those differences. If that average is significantly greater than zero, there is an interaction. E.Take the difference between 5 and 4 and 3 and 2, then subtract those differences. Because that result is 0, there is not an interaction.Take the difference between 5 and 4 and 3 and 2, then subtract those differences. Because that result is 0, there is not an interaction.

176. Darkness of Background DarkLight Text color BlackBlack (A) Black (B) WhiteWhite (C) White (D) Click on the calculation that would give you the simple main effect of text color on dark backgrounds: A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

177. Darkness of Background DarkLight Text color BlackBlack (A) Black (B) WhiteWhite (C) White (D) Click on the calculation that would give you the simple main effect of text color on light backgrounds: A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

178. Darkness of Background DarkLight Text color BlackBlack (A) Black (B) WhiteWhite (C) White (D) Click on the calculation that would give you the overall main effect of text color: A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

179. Darkness of Background DarkLight Text color BlackBlack (A) Black (B) WhiteWhite (C) White (D) Click on the calculation that would give you the simple main effect of background in the black text condition: A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

180. Darkness of Background DarkLight Text color BlackBlack (A) Black (B) WhiteWhite (C) White (D) Click on the calculation that would give you the simple main effect of background in the white text condition: A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

181. Darkness of Background DarkLight Text color Black White Click on the calculation that would give you the overall main effect of background: A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

182. Darkness of Background DarkLight Text color BlackBlack (A) Black (B) WhiteWhite (C) White (D) If the two simple main effects for text color are the same (i.e., A-C = B-D), there is no interaction. A. True B. False A. True B. False A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

183. Darkness of Background DarkLight Text color BlackBlack (A) Black (B) WhiteWhite (C) White (D) If the two simple main effects of background are the same (i.e., A-B = C-D), there is no interaction. A. True B. False A. True B. False A C A- B B D A- C Average of A-C and B- D B - D C - D Average of A-B and C- D

184. Background DarkLight Text color WhiteWhite (A)White (B) GrayGray (C)Gray (D) If the simple main effects of 2 different factors differ (as in the example below), there is an interaction. 5 3 1 (A- B); (5-4) 4 2 2 (A-C); (5-3) 2 (B-D); (4-2) 1 (C – D); (3-2) True False

185. BackgroundOverall background main effect DarkLight Text color White Gray Overall text color main effect If the overall main effects of 2 different factors differ (as in the example below), there is an interaction. 5 3 1 4 2 True False 2

186. Background DarkLight Text color WhiteWhite (A)White (B) GrayGray (C)Gray (D) If the simple main effects of the same factor differ (as in the example below), there is an interaction. 5 4 1 ( A- B); (5-4) 4 2 1 (A-C); (5-4) 2 (B-D); (4-2) 2(C – D); (4-2) True False

187. Get your results