Reliability

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# Reliability - PowerPoint PPT Presentation

Reliability. Consistent Dependable Replicable Stable . Two Administrations. Test/retest same test - same group Parallel/Alternate forms different versions of test - same group. Two administration procedure:. Administer tests (in two sessions) Convert to z scores (if necessary)

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## PowerPoint Slideshow about 'Reliability' - rasul

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Presentation Transcript
Reliability
• Consistent
• Dependable
• Replicable
• Stable
• Test/retest

same test - same group

• Parallel/Alternate forms

different versions of test - same group

• Administer tests (in two sessions)
• Convert to z scores (if necessary)
• Correlate (Pearson or Spearman)
• Problems?????
• Duration between????
• Type of variable?????
• One test
• One group
• 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
• Internal consistency of items
• What types of tests to use this on???
Inter item consistency
• Statistical estimation
• Kuder-Richardson Formula 20 (KR20) = dichotomous questions
• Cronbach alpha (alpha coefficient) = all questions
• (factor analysis)
Reliability coefficient
• 0.00 - 1.00
• higher is better
• score is relative, not absolute
Inter-rater reliability
• Consensus between raters
• Percentage of agreement
• Kappa statistic (2 or many raters)
Threats to reliability
• Construction