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Evaluating Psychological Tests

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Evaluating Psychological Tests Psychological testing Suffers a credibility problem within the eyes of general public Two main problems Tests used inappropriately ... – PowerPoint PPT presentation

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Title: Evaluating Psychological Tests


1
Evaluating Psychological Tests
2
Psychological testing
  • Suffers a credibility problem within the eyes of
    general public
  • Two main problems
  • Tests used inappropriately
  • Goddard (1912) used a translation of Binets test
    to test ability of American immigrants -
    conclusion 79 of Italian immigrants
    feeble-minded - bias
  • Tests themselves can be flawed
  • Often measures supposed constructs which are not
    supported by proper factor analysis - (Internal
    locus of control)

3
External bias in tests
  • Do group differences imply test bias (difficulty
    unrelated to characteristic being assessed)?
  • V1 - innate abilities can be different across
    groups (Reynolds, 1995 Kline, 1993)
  • Japanese have higher than average spatial
    abilities
  • African Americans have lower IQ (Hernstein
    Murray, 1996)
  • V2 Ethnic and gender groups must have the same
    underlying abilities evidence to the contrary
    must be a product of measuring something other
    than what is relevant
  • Kline egalitarian fallacy

4
Dealing with differences
  • Detected through different regression equation
    not through different means
  • What purpose does research in this area serve?
  • Within group differences far outweigh between
    group differences

5
Detecting internal bias
  • If only gross scores are considered, hard and
    easy items for each group might balance
    themselves out giving a false impression of the
    tests health
  • Alternative Run a mixed factorial ANOVA
  • Each test item (question) is entered as a level
    of repeated measures factor
  • Group between subjects variable
  • Main effect of item expected
  • Main effect of group shows external bias
  • Interaction show internal bias in that the
    pattern of responding is different across the
    groups
  • Such a method is susceptible to power manipulation

6
Bias - performance characteristics
  • Response bias
  • individuals are more likely to agree than
    disagree (Cronbach, 1946) response set of
    acquiescence
  • Does not cause a problem if everyone behaves in
    same manner standard score will be unaffected
  • But there are considerable individuals
    differences in acquiescence therefore it can
    cause a major problem
  • Changing polarity removes this difficulty
  • Social desirability
  • Counter acted by lie scales and consistency
    measures

7
Obvious influences
  • Motivation
  • Expectation
  • Anxiety
  • Test specific practise

8
Revisiting Validity
9
Validity different definitions
  • Correctness or truth of an inference
  • Validity with respect to IV
  • Are we truly manipulating that which we think we
    are
  • Often relies on the construct of interest being
    adequately described
  • How do you manipulate something like the
    unconscious?
  • Validity with respect to the DV
  • Extent to which you are measuring what you claim
    to measure

10
Different types of validity
  • Content validity
  • Whether the target construct is adequately
    addressed
  • When measuring depression should assess aspects
    such as fatigue, anxiety, appetite, motivation,
    libido
  • Is assessed through expert opinion
  • Has a certain amount of subjectivity

11
Different types of validity
  • Criterion-Related validity
  • How measure compares to some already validated
    measure
  • Two types
  • Predictive
  • Concurrent

12
Different types of validity
  • Construct validity
  • Most important Are the experimental
    manipulations that we make really manipulating
    the construct of interest
  • Evaluation requires
  • Clear definition of the construct
  • Can be difficult e.g., IQ has many different
    facets
  • Assess match between construct and operations
    used to represent it (exp manipulations)
  • Can involve criterion and content validity
  • Viewed as an evolving never ending process

13
Different types of validity
  • Internal validity degree to which the
    independent and dependent variables are causally
    linked
  • External validity degree to which causal
    relationship holds across different settings

14
How relevant is validity to you
  • Reviewing articles is essentially addressing
    validity and reliability issues
  • In examination situation would be useful although
    not essential to talk about the different forms
    of validity
  • In discussion sections of reports again you are
    essentially evaluating the results with respect
    to validity and reliability
  • Would not really use the formal language used
    here is a style issue
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