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Reliability - PowerPoint PPT Presentation


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Reliability. Consistent Dependable Replicable Stable . Threats to reliability. Construction Administration (tester, testee, environment) Scoring Interpretation . Two Administrations. Test/retest same test - same group Parallel/Alternate forms

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Presentation Transcript
reliability
Reliability
  • Consistent
  • Dependable
  • Replicable
  • Stable
threats to reliability
Threats to reliability
  • Construction
  • Administration (tester, testee, environment)
  • Scoring
  • Interpretation
two administrations
Two Administrations
  • Test/retest

same test - same group

  • Parallel/Alternate forms

different versions of test - same group

two administration procedure
Two administration procedure:
  • Administer tests (in two sessions)
  • Convert to z scores (if necessary)
  • Correlate (Pearson or Spearman)
two administration issues
Two administration issues:
  • Problems?????
  • Duration between????
  • Type of variable?????
one administration
One Administration
  • One test
  • One group
  • One administration
one administration procedure
One administration procedure:
  • Administer test to one group
  • Divide questions to score
  • Split Half
    • first/second or odd/even halves????
  • Correlate scores from halves
  • Apply Spearman-Brown formula
    • estimate changes in length
uses of one administration
Uses of one administration:
  • Internal consistency of items
  • Appropriate for homogenous tests
  • Not appropriate for heterogeneous tests
    • (may have several measures within test)
inter item consistency
Inter item consistency
  • Statistical estimation
  • Kuder-Richardson Formula 20 (KR20) = dichotomous questions
  • Cronbach alpha (alpha coefficient) = all questions
  • (factor analysis)
reliability coefficient
Reliability coefficient
  • 0.00 - 1.00
  • higher is better
  • score is relative, not absolute
inter rater reliability
Inter-rater reliability
  • Consensus between raters
  • Percentage of agreement
  • Kappa statistic (2 or many raters)
project homework
Project homework
  • Which approach(s) would you use to determine the reliability of your measure?

-- Why did you select those approach(s)?