1. How to Start This PowerPoint® Tutorial
Before getting started, you need to know 3 things:
If you are given the option to click on a button that says “Enable Content,” “Enable Macros,” or “Enable Editing,” please do so. That button may appear at the top of your screen and look like this:
Run this presentation in PowerPoint’s “Slide Show” mode. One way to get into “Slide Show” mode is to click on the “Slide Show” tab and select “From Beginning.” Alternatively, you could click on the button near the bottom of your screen that looks like a picture of a computer monitor (it looks like the icon we have highlighted below in yellow).
Once in “Slide Show” Mode, click the green button below to go to
the next slide. On the next slide, you will again click on a green button.
This button will work once you are in PowerPoint’s slide show mode

2. Visualizing an Experiment That Manipulates Two Variables: Part 3
Click here to begin!
If the green button above does not work, quit Powerpoint®.
Then, restart Powerpoint. When Powerpoint restarts,
be sure to click any buttons that say “Enable macros.”
Then, put the program in “Slide Show” mode.
Quit
© 2016 Mark Mitchell & Janina Jolley

3. What This Tutorial Can Do For You
If you did the previous tutorial, you learned how to average a factor’s simple main effects to estimate that factor’s overall main effect and how to subtract a factor’s simple main effects to estimate the factor’s interaction effect: the degree to which its effect is affected by the other manipulated factor. In this tutorial, you will learn how to interpret graphs of the results of factorial experiments.
To continue, click your keyboard’s right arrow button.

4. Working Through the Tutorial
The first time through the tutorial, you should click through the slides (you can use either the right arrow button or your mouse)—except when you are asked a question. When you are asked a question, you should answer it.
After your first time through the tutorial, you can use the “Menu” slide to skip to a particular part of the tutorial. The “Menu” slide is the next slide, but you can always get to the Menu by clicking on the orange “home” button on the bottom left of any slide.
To continue, click your keyboard’s right arrow button.

5. Choose an item from the menu below—or just click your keyboard’s right arrow button.
Making graphs of 2 X 2 factorial experiments
Interpreting graphs of 2 X 2 factorial experiments
Quiz
Quit

6. 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
To continue, click your keyboard’s right arrow button.

7. ***** **** *** ** * ■ * From table to graph: Dark Light Background
Look at the table below.
Click the black text row of that table to see that row converted into a line on the graph to the right.
Then, click on the white text row to see that row graphed.
*****
**** *** **
* ■
Dark Light
Background
Black text ■ ■ ■
White text *
Dark background
Light
background
Black
Text
White
***
***
****
****
*** *
To continue, click your keyboard’s right arrow button.
*** *

8. Background Dark Light Text color Black ** **** White *** *
Plot the points by clicking on the four individual cells (the four places that say “Plot me”).
Background
Dark
Light
Text color
Black **
****
White
*** *
Plot me
Plot me
Plot me
***
Plot me
*****
*** ◊ ◊ *
Dark Light
Background
**** ■
Black text
***
White text ■ **
To continue, click your keyboard’s right arrow button.

9. 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 such 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
To continue, click your keyboard’s right arrow button.

10. Two parallel lines are so much alike. Too bad they will never met.
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.

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

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

13. Does this graph suggest an interaction between text and
background?
Yes
*****
****
***
** * * No
Red text
Blue text
Dark Light
Background

14. Remember, if the lines are not parallel, there may be an interaction.
Does this graph suggest an interaction between text and
background?
Yes No
*****
****
*** ** *
Red text
Remember, if the lines are not parallel, there may be an interaction.
Blue text
Dark Light
Background

15. Does this graph suggest an interaction between text and
background?
Yes No
*****
****
*** **
Blue text
Red text
Dark Light
Background

16. 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. Do these results suggest a main effect for text color such that blue text is more readable than red text?
Yes No
*****
****
***
** * *
Blue text
Red text
Dark Light
Background

17. 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.
True
*****
****
***
** * *
False
Blue text 
Red text 
Dark Light
Background

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

19. This graph suggests no main effects or interactions.
True
False
*****
****
*** ** *
Dark Light
Background
White text line * *
Black text line

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

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

22. ***** **** *** ** * * 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.
True
*****
****
***
** * *
Red text
False
Blue text
Dark Light
Background

23. In this case, is there is a main effect for background?
Yes No
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?
*****
****
***
** * *
Red text  
Blue text
Dark Light
Background

24. Does the graph below suggest a main effect of 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).
To average the lines, put a dot between the left ends of the two lines. Then, put dot between the right ends of the two lines. Finally, draw a line between those dots.
Yes No
*****
**** *
*** **
** * *
Dark Light
Background
Black text
Yellow text

25. 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).
True
*****
****
***
** * *
Red text
False
Blue text
Dark Light
Background

26. ***** **** * *** ** * * * 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.
*****
****
***
** * *
True
Red text *
Blue text
False *
Dark Light
Background

27. 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).
*****
****
***
** * *
True
Red text
False
Blue text
Dark Light
Background

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

29. 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.
Click if you want a hint
True
False
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?
*****
****
***
** * *
Red text
Blue text
Black Green
Background

30. Yes No ***** **** *** ** * *
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 a main effect for text color and an interaction.
Yes No
*****
****
***
** * *
1. Is the red line above the blue line, indicating a main effect for text color? (If you are stuck, compare the midpoints of the two lines).
2. Is the superiority of red text over blue text greater in the black background condition than in the green background condition, indicating an interaction?
Red text
Blue text
Black Green
Background

31. Yes No ***** **** *** ** * *
From the graph, it appears we have a main effect for background.
Yes No
*****
****
***
** * *
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?
Red text
Blue text
Black Green
Background

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

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

34. Does this graph suggest a main effect for background?
Yes No
Is the mid-point of the left end of the two lines higher than the mid-point of the right end of the two lines? In other words, on average, are the lines higher on the left (black background) side of the graph than on the right (green background) side?
*****
****
***
** * *
White text 
Yellow text 
Black Green
Background

35. Does this graph suggest an interaction between text
color and background color?
Yes 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?
Blue text
Yellow text
White Black
Background

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

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

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

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

40. * * * * No No Yes Yes ***** **** *** ** * Dark Light Background
Click on the two points you would have to compare to see the simple main effect of text in the dark background conditions. No
*****
****
*** ** *
Dark Light
Background *
Black text No * *
Yes
White text *
Yes
Once you see two “yes” boxes, click your keyboard’s right arrow button.

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

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

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

44. 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.
To continue, click your keyboard’s right arrow button.

45. * * 6 6 3 3 Blue Text Color Green Bold (Thick lines)
Click on the 4 numbered buttons at the bottom of the screen to see the 4 simple main effects.
Blue 6 * 6 +3 +3
Text
Color 3 * 3
Green
Bold (Thick lines)
Normal (Thin lines)
Font style
#1 Simple main effect for text color in the normal ( thin line) conditions
#2 Simple main effect for text color in the bold (thick line) conditions
# 3 Simple main effect for font style in the blue line condition
#4 Simple main effect for font style in the green line condition
After you have clicked all 4 buttons, click your keyboard’s right arrow button.

46. Click on the 3 blue buttons to see what effects this graph reveals.6 6
Is there a main effect for line color?
Blue *
Text
Color
Is there a main effect for line thickness? 3 * 3
Green
Bold
(Thick lines)
Normal
(Thin lines)
Is there an interaction between line color and line type?
Font 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.
After you have clicked all 3 buttons, click your keyboard’s right arrow button.
No, the green and blue lines are parallel, showing that they are changing at the same rate.

47. Does there seem to be a color main effect?
Yes No 7 6
Blue
Yes, the blue line is above the green line.
Text
Color 4 3
Green
Normal
Bold
Font type
To continue, click your keyboard’s right arrow button.

48. Yes No 7 6 4 3 Does there seem to be a main effect for font? Blue Text
Yes, the normal font side of the graph is
lower than the bold font side of the graph.
Text
Color 4 3
Green
To continue, click your keyboard’s right arrow button.
Bold
Normal
Font type

49. Does there seem to be an interaction between color font?
Yes No 7 6
Blue
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.
Text
Color 4 3
To continue, click your keyboard’s right arrow button.
Green
Bold
Normal
Font type

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

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

52. 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 main effect for text color
A main effect for font
An interaction between text color and font A B C 6 * 6
Blue
Text
Color 4 * 4
Green
Bold
text
Normal text
Font

53. 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
Slope up, indicating a main effect for line thickness
Slope up, indicating a main effect for color
Go neither up nor down, suggesting no effect for line
thickness A B C 6 6
Blue
Text
Color 4 4
Green
Thick lines
Thin lines
Line type

54. 5 4 3 2 In the experiment tabled below, what is the simple main
effect of line thickness in the blue text conditions? 1 2 3 4 5 5 +2 4
Blue
Text
Color 3 2
Green
Thin
Thick
Line Thickness

55. 5 4 3 2 In the experiment tabled below, what is the simple main
effect of line thickness in the green text conditions? 1 2 3 4 5 5 4
Blue +2
Text
Color 3 2
Green
Thin
Thick
Line Thickness

56. 5 3 4 2 What is the simple main effect of color (blue vs. green)
in the thin line conditions? 1 2 3 4 5 5 3 4
Blue +1
Text
Color 2
Green
Thin
Thick
Line Thickness

57. 5 3 4 2 What is the simple main effect of color (blue vs. green)
in the thick line conditions? 1 2 3 4 5 5 +1 3
Blue 4
Text
Color 2
Green
Thin
Thick
Line Thickness

58. 5 3 4 2 What is the overall (average) main effect of color
(blue vs. green) across all conditions? 1 2 3 4 5 5 3
Blue
Text
Color 4 2
Green
Thin
Thick
Line Thickness

59. 5 3 4 2 What is the overall, average main effect of line
thickness across all conditions? 1 2 3 4 5 5 3
Blue 4
Text
Color 2
Green
Thin
Thick
Line Thickness

60. 5 4 3 2 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? 5
Yes No 4
Blue 3
Text
Color 2
Green
Thin
Thick
Line Thickness

61. 5 3 4 2 Was there an interaction involving line thickness
and text color?
Yes No 5 +2 3
Blue 4 +2
Text
Color 2
Green
Thin
Thick
Line thickness

62. Was the main effect for line thickness (normal vs
Was the main effect for line thickness (normal vs. bold) the same as the main effect for text color (green vs. blue)?
Yes
No–and there is no interaction
No–and there is an interaction A 5 B C 4
Blue 3
Text
Color 2
Green
To continue, click your keyboard’s right arrow button.
Normal
Bold
Font type

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

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

65. Yes No 4 4 3 3 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 4 4
Blue
Text
Color 3
Green 3
Thin (Normal)
Thick (Bold)
Line Thickness
(Normal vs. Bold Text)

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

67. Yes No 4 4 3 3 Is there an overall main effect line thickness?
Correct. The average height of
the thin and thick lines are
not different. 4 4
Blue
Text
Color 3
Green 3
Thin
Thick
To continue, click your keyboard’s right arrow button.
Line Thickness

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

69. To determine the simple main effect of line thickness in the blue condition, you would
Take the difference between 5 and 4.
Take the difference between 3 and 2.
Take the difference between 4 and 2.
Take the difference between 5 and 3.
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 subtract those differences. 4
Blue 5
Text
Color 2 3
Green
Thin
Thick
Line Thickness

70. To determine the simple main effect of line thickness in the green condition, you would
Take the difference between 5 and 4.
Take the difference between 3 and 2.
Take the difference between 4 and 2.
Take the difference between 5 and 3.
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 subtract those differences. 4
Blue 5
Text
Color 2 3
Green
Thin
Thick
Line Thickness

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

72. 4 5 2 3 To find the interaction between line thickness and color,
Take the difference between 5 and 4.
Take the difference between 3 and 2.
Take the difference between 5 and 3.
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 subtract those differences. Because that result is 0, there is not an interaction. 4
Blue 5
Text
Color 2 3
Green
Thin
Thick
Line Thickness

73. Get your results