1. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter Two Statistics and the Research Process

2. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 2 Scientific Research The goal of science is to understand the “laws of nature” We examine a specific influence on a specific behavior in a specific situation Then, we generalize back to the broader behaviors and laws with which we began

3. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Scientific Research Samples and Populations Relationships Descriptive and Inferential Statistics Experiments and Correlations

4. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Variables Quantitative and Qualitative Scales of Measurement Discrete, Continuous, or Dichotomous

5. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Research: Samples and Populations

6. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 6 Samples and Populations The entire group of individuals to which a law applies is the population –Ex: All men and women in the U.S. A sample is a relatively small subset of a population that is intended to represent, or stand for, the population –Ex: Men and women who were weighed by CDC The individuals measured in a sample are called the participants or subjects

7. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 7 Drawing Inferences We use the scores in a sample to infer or to estimate the scores we would expect to find in the population.

8. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 8 Representativeness In a representative sample, the characteristics of the sample accurately reflect the characteristics of the population.

9. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 9 Random Sampling Random sampling is a method of selecting a sample in which the individuals are randomly selected from the population.

10. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 10 Unrepresentative Samples Random sampling should result in a sample that is representative of the population, but it is not foolproof An unrepresentative sample can result in misleading evidence and wrong conclusions

11. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Research: Relationships

12. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 12 Examining Relationships In a relationship, as the scores on one variable change, the scores on the other variable change in a consistent manner.

13. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 13 Strength of a Relationship The strength of a relationship is the degree of consistency in the relationship A stronger relationship occurs when one group of similar Y values is associated with one X score and a different group of similar Y scores is associated with the next X score

14. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 14 Factors Affecting Strength A “weaker” relationship may be due to additional extraneous influences and/or individual differences Individual differences refer to the fact no two individuals are identical

15. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 15 Graphing Relationships Describe a relationship using the general format: –“Scores on the Y variable change as a function of changes in the X variable.” –The given variable in a study is the X variable.

16. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 16 Four Sample Graphs A graph showing a perfectly consistent association.

17. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 17 Four Sample Graphs A relationship that is not perfectly consistent.

18. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 18 Four Sample Graphs A weak relationship.

19. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 19 Four Sample Graphs No consistent pattern.

20. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Research: Descriptive and Inferential Statistics

21. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 21 Descriptive Statistics Descriptive statistics are procedures used for organizing and summarizing data. –What scores occurred? –What is the average or typical score? –Are the scores very similar to each other or very different? –Is a relationship present? Example: People in the U.S weigh much more now than they did four decades ago (CDC, 2004)

22. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 22 Inferential Statistics Inferential statistics are procedures for deciding whether sample data accurately represent a particular relationship in the population Inferential statistics allow us to make inferences about the scores and relationship found in the population –Example: If the average weight of U.S citizens continues to increase as in the past, then most people will be considered overweight in the next 40 years by today’s standards.

23. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 23 Statistics and Parameters A statistic is a number that describes a characteristic of a sample of scores A parameter is a number that describes a characteristic of a population of scores

24. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 24 Descriptive and Inferential Statistics In order to know which descriptive or inferential statistic to use, you must first determine the design of the study and the scale of measurement of your variables.

25. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 25 Research Designs A study’s design is the way the study is laid out There are two major types of designs: –Experiments –Correlational studies

26. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 26 Variables A variable is anything that, when measured, can produce two or more different values (scores). Some common variables are: –Age –Race –Gender –Intelligence –Personality type

27. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 27 Types of Variables A quantitative variable indicates the amount of a variable that is present A qualitative variable classifies an individual on the basis of some characteristic

28. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Research Design: Experiments vs. Correlations

29. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 29 Experiments In an experiment, the researcher actively changes or manipulates one variable and then measures participants’ scores on another variable to see if a relationship is produced.

30. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 30 The Independent Variable The independent variable is the variable that is changed or manipulated by the experimenter A condition is a specific amount or category of the independent variable that creates the specific situation under which participants are examined

31. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 31 The Dependent Variable The dependent variable is used to measure a participant’s behavior under each condition of the independent variable We apply descriptive statistics only to the scores from the dependent variable

32. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 32 Correlational Studies In a correlational study, we simply measure participants’ scores on two variables and then determine whether a relationship is present.

33. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 33 Causality We cannot definitively prove the independent variable causes the scores on the dependent variable to change. It is always possible some other hidden variable is actually the cause.

34. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. The counseling department examined the stress levels of students by randomly choosing 100 students to interview at your university. The average stress level was 18 on a scale of 1-50. It was concluded that students at your university have moderately high stress levels. 1.What is the sample? population? 2.What is the descriptive statistic? inferential statistic? 3.Was this an experiment or correlation?

35. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 35 Variables

36. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 36 Characteristics of Variables Two important characteristics of variables are –The type of measurement scale involved –Whether it is continuous or discrete

37. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 37 Measurement Scales There are four types of measurement scales: –A nominal scale does not indicate an amount; rather, it is used for identification, as a name. –An ordinal scale indicates rank order. There is not an equal unit of measurement separating each score.

38. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 38 Measurement Scales (cont’d) –An interval scale indicates an actual quantity and there is an equal unit of measurement separating adjacent scores. Interval scales do not have a “true” 0. –A ratio scale reflects the true amount of the variable that is present because the scores measure an actual amount, there is an equal unit of measurement, and 0 truly means that zero amount of the variable is present.

39. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 39 Discrete and Continuous Any measurement scale also may be either continuous or discrete A continuous scale allows for fractional amounts and so decimals make sense In a discrete scale, only whole-number amounts can be measured

40. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Dichotomous Variable A dichotomous variable has only two possible categories or scores: –Male or female –Yes or no –Correct or incorrect Chapter 2 - 40

41. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Three female students complete a Stroop test. Lorna finishes in 12.67 seconds; Desiree finishes in 14.87; and Marianne in 9.88. Are these data discrete or continuous? Is the variable a(n) nominal, ordinal, interval or ratio observation? On an ordinal scale, what is Lorna’s score?

42. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 42 Summary of Measurement Scales

43. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 43 Key Terms Chapter 1 - 43 as a function of condition continuous scale correlational study dependent variable descriptive statistics design dichotomous variable discrete scale experiment independent variable individual differences inferential statistics interval scale level nominal scale ordinal scale parameter participant population

44. © 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 2 - 44 Key Terms (Cont’d) Chapter 1 - 44 ratio scale relationship sample statistic strength of a relationship treatment variable