Variables Used in Experimentation ?

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Variables Used in Experimentation ?
Chapter 6
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• Types of Variables ?
• The Independent Variable ?
• The Dependent Variable ?
• Demo Identifying IVs and DVs ?

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6.1 Types of Variables
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• Variable
• Any characteristic or phenomenon that can vary
• across organisms, situations, or environments
• IV-DV-EV
• IV independent variable ???
• DV dependent variable ???
• EV extraneous variable ????
• Discrete vs. Continuous Variables
• Qualitative vs. Quantitative Variables

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6.2 The Independent Variable
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• 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
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• 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?
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6.2.2 Establishing Variation in the IV
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• 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?
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6.2.3 Constructing the IV
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• 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?
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6.2.4 Number of IV
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• More than one provided additional information
• Theoretically no limit to the number that can be
  used
• Practically there is a limit

6.2?
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6.3 The Dependent Variable
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• 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
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• 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 ?
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6.3.1 Response to be Used as a DV -1
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• 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 ?
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6.3.1 Response to be Used as a DV -2(end)
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• How to choose
• Previous experimentation can help
• More commitment demand
• (e.g.) Like liking rating scale
• roommate

6.3 ?
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6.3.2 Reducing Participant Error
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• 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 ?
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6.3.3 Number of DVs -1
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• 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 ?
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6.3.3 Number of DVs -2(end)
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• Analysis Multivariate
• Multidimensional Statistical Analysis
• Multivariate Analysis of Variance (error rate)

6.3 ?
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Demo Identifying IVs and DVs
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• 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 ?
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• Asch conducted an experiment in which he
  wanted to determine if a persons 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 ?
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• 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 ?
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• 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.