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Unformatted text preview: Today *Admin *Spring Break next week! *Paper 2 to be handed back in lecture on Mon, Mar 24 *Reliability and Validity Last Time *Hypothesis Testing Review Reliability and Validity *Validity = accuracy *actually studying the variables intended to be manipulated or measured *Reliability = consistency and dependability *the consistency, stability, or repeatability of a behavior Reliability *Is there consistency and consensus in what variable measures? *A watch that runs correctly but is set 94 minutes fast is low in validity, but high in reliability Perfect Reliability *Perfect reliability means that the scores are perfectly consistent. Good Reliability *Reliability deteriorates when the consistency is lost. *Here the rank orderings are still reasonably consistent. Fair Reliability *As reliability deteriorates further, the rank orderings from the two testings are less similar. Methods of Assessing Reliability *Test-retest *Interrater reliability *Interitem reliability *Internal consistency *Split-half *Cronbach’s alpha Measurement Error *measurement error *inaccuracy that exists when measuring a characteristic or behavior Effect of Measurement Error *X = T + e *Note that the average isn’t affected by random error…only the variability Validity *Does variable measure what it’s supposed to? *A watch that tells good time has high validity *A watch that runs correctly but is set 94 minutes fast has low validity *A broken watch will be valid twice a day Validity *Does variable measure what it’s supposed to?*Does variable measure what it’s supposed to?...
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This note was uploaded on 03/26/2008 for the course PSYCH 31 taught by Professor Dicorcia during the Spring '08 term at Tufts.
- Spring '08
- Experimental Psychology