Variables Used in Experimentation ♣

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

2. 6.1 Types of Variables Back to Chapter Contents 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

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

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

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

6. 6.2.3 Constructing the IV Back to Chapter Contents • 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 6.2⊲

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

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

9. 6.3.0 The Dependent Variable: Introduction Back to Chapter Contents • 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 6.3 ◄

10. 6.3.1 Response to be Used as a DV -1 Back to Chapter Contents • 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 6.3 ◄

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

12. 6.3.2 Reducing Participant Error Back to Chapter Contents • 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 6.3 ◄

13. 6.3.3 Number of DVs -1 Back to Chapter Contents • 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 6.3 ◄

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

15. Demo: Identifying IVs and DVs Back to Chapter Contents • 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

16. Research Sample Ⅰ Back to Chapter Contents 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.

17. Research Sample Ⅱ Back to Chapter Contents 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.

18. Research Sample Ⅲ Back to Chapter Contents 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.