1. Reliability n Consistent n Dependable n Replicable n Stable

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

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

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

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

6. One Administration One test One test One group One group One administration 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: n Internal consistency of items n Appropriate for homogenous tests n Not appropriate for heterogeneous tests u (may have several measures within test)

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

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

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

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