1. Chapter 6 Variables Used in Experimentation ♣ ♣ Types of Variables   The Independent Variable   The Dependent Variable   Demo: Identifying IVs and DVs    Back to Brief Contents

2. 6.1 Types of Variables Variable Any characteristic or phenomenon that can vary across organisms, situations, or environments IV-DV-EV IV: independent variable 獨變項 DV: dependent variable 依變項 EV: extraneous variable 外部變項 Discrete vs. Continuous Variables Qualitative vs. Quantitative Variables  Back to Chapter Contents

3. 6.2 The Independent Variable 6.2.1 Variation 6.2.1 6.2.2 Establishing Variation in the IV 6.2.2 6.2.3 Constructing the IV 6.2.3 6.2.4 Number of IV 6.2.4  Back to Chapter Contents

4. 6.2.1 Variation Presence versus Absence Fig 6.1 Amount of a Variable Fig 6.2 Number of levels? Type of a Variable Fig 6.3  Back to Chapter Contents 6.2 ⊲

5. 6.2.2 Establishing Variation in the IV Summary : Fig 6.4Fig 6.4 Experimental Manipulation  Manipulation of Instructions Dangers: inattentive, misinterpretation, forgetfulness  Manipulation of Events Advantages: more realistic, more impact Individual Difference Manipulation  Back to Chapter Contents 6.2 ⊲

6. 6.2.3 Constructing the IV Must translate the independent variable into concrete operational terms  Easy with some IVs Drugs Length of Time (exposure time) Lesion: area of the brain  Hard with others Aggression Delay of gratification  Back to Chapter Contents 6.2 ⊲

7. 6.2.4 Number of IV More than one provided additional information Theoretically no limit to the number that can be used Practically there is a limit  Back to Chapter Contents 6.2 ⊲

8. 6.3 The Dependent Variable 6.3.0 Introduction 6.3.0 6.3.1 Response to be Used as a DV 6.3.1 6.3.2 Reducing Participant Error 6.3.2 6.3.3 Number of DV 6.3.3  Back to Chapter Contents

9. 6.3.0 The Dependent Variable: Introduction Definition Behavioral variable designed to measure the effect of the variation of IV Requirement Sensitive to, or able to pick up the effects of IV (e.g.) split-brain Indicate: facilitating or inhibiting Gender Gender-neutral measure Responding : truthful vs. cooperating  Back to Chapter Contents 6.3 ◄

10. 6.3.1 Response to be Used as a DV -1 Sensitivity: to the effect of IV Difficulty  The processes, attributes, or outcome are not directly observable  Select observation to allow inference back to the construct (e.g.) Learning: increase in performance  Back to Chapter Contents 6.3 ◄

11. 6.3.1 Response to be Used as a DV -2(end) How to choose  Previous experimentation can help More “commitment” demand (e.g.) Like: liking rating scale roommate  Back to Chapter Contents 6.3 ◄

12. 6.3.2 Reducing Participant Error Disguise the measure & guard against: cooperation Techniques: 1. Outside the context of the exp. 2. Assess behavior of significance to the P (commitment) 3. P not realize the DV observed (e.g. natural beh.) 4. Embed key items in a larger questionnaire 5. Disguise the reason for interest (hypothesis) 6. “Whoops” procedures 7. Confederate 8. Physiological measure: not under conscious control  Back to Chapter Contents 6.3 ◄

13. 6.3.3 Number of DVs -1 More than one DV used  (e.g.) Learning: frequency; amplitude; latency  (e.g.) Attitude: questionnaire, observing behavior, physiological measure If highly correlated  Identical measures: all but one can be dropped If not highly correlated: ask why not  Unreliability  Not measure the same aspect of the construct  Back to Chapter Contents 6.3 ◄

14. 6.3.3 Number of DVs -2(end) Analysis: Multivariate  Multidimensional Statistical Analysis  Multivariate Analysis of Variance (error rate)  Back to Chapter Contents 6.3 ◄

15. Demo: Identifying IVs and DVs For each of the following research examples, identify  A. The independent variable  B. The levels of the independent variable  C. The method used to manipulate the independent variable  D. The dependent variable  Back to Chapter Contents

16. Research Sample Ⅰ Asch conducted an experiment in which he wanted to determine if a person’s impression of another person is influenced more by information received immediately after being introduced or by information received later in the conversation. Asch presented a series of positive and negative adjectives to two groups of individuals. One group received the positive adjectives first and the other group received the negative adjectives first. After reading both lists of adjectives, each group gave their impression of the hypothetical person.  Back to Chapter Contents

17. Research Sample Ⅱ A study was conducted to determine if men think the women in a bar get more attractive as closing time approaches. This was a field study in which the researcher asked patrons of the bar to evaluate the attractiveness of various women in the bar at four different times in the evening, with the last evaluation being ten minutes prior to closing.  Back to Chapter Contents

18. Research Sample Ⅲ Benbow and Stanley wanted to find out if gender could be used in trying to differentiate mathematical ability, so they compared the test scores on the mathematical portion of the SAT of 9,927 seventh- and eight-grade boys and girls. In this study they used only the scores of boys and girls who had the same number of mathematics courses. When they compared the SAT mathematics test scores of the boys and girls, they found that the boys scored significantly higher than the girls. In addition, they found that more than 50 percent of the boys scored above 600, whereas none of the girls scored that high.  Back to Chapter Contents