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Reliability

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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Reliability

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  1. Reliability • Consistent • Dependable • Replicable • Stable

  2. Threats to reliability • Construction • Administration (tester, testee, environment) • Scoring • Interpretation

  3. Two Administrations • Test/retest same test - same group • Parallel/Alternate forms different versions of test - same group

  4. Two administration procedure: • Administer tests (in two sessions) • Convert to z scores (if necessary) • Correlate (Pearson or Spearman)

  5. Two administration issues: • Problems????? • Duration between???? • Type of variable?????

  6. One Administration • One test • One group • One administration

  7. 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

  8. Uses of one administration: • Internal consistency of items • Appropriate for homogenous tests • Not appropriate for heterogeneous tests • (may have several measures within test)

  9. Inter item consistency • Statistical estimation • Kuder-Richardson Formula 20 (KR20) = dichotomous questions • Cronbach alpha (alpha coefficient) = all questions • (factor analysis)

  10. Reliability coefficient • 0.00 - 1.00 • higher is better • score is relative, not absolute

  11. Inter-rater reliability • Consensus between raters • Percentage of agreement • Kappa statistic (2 or many raters)

  12. Project homework • Which approach(s) would you use to determine the reliability of your measure? -- Why did you select those approach(s)?

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