Chapter 6Variables Used in Experimentation ♣

Types of Variables The Independent Variable The Dependent Variable Demo: Identifying IVs and DVs

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6.1 Types of Variables

VariableAny 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

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6.2 The Independent Variable

6.2.1 Variation

6.2.2 Establishing Variation in the IV

6.2.3 Constructing the IV

6.2.4 Number of IV

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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

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6.2⊲

6.2.2 Establishing Variation in the IV

Summary: Fig 6.4

Experimental Manipulation Manipulation of Instructions

Dangers: inattentive, misinterpretation, forgetfulness

Manipulation of Events Advantages: more realistic, more impact

Individual Difference Manipulation

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6.2⊲

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

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6.2⊲

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

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6.2⊲

6.3 The Dependent Variable

6.3.0 Introduction

6.3.1 Response to be Used as a DV

6.3.2 Reducing Participant Error

6.3.3 Number of DV

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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

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6.3 ◄

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

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6.3 ◄

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

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6.3 ◄

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

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6.3 ◄

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

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6.3 ◄

6.3.3 Number of DVs -2(end)

Analysis: Multivariate Multidimensional Statistical Analysis Multivariate Analysis of Variance (error

rate)

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6.3 ◄

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

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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.

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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.

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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.

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