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Reliability and Validity. What is Reliability?. A measure is considered reliable when: there is very little error in the measurement Measurement remains constant under specific conditions. Types of Error. Random Systematic. Effect of Unreliable Measures. Meaningless results
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What is Reliability? • A measure is considered reliable when: • there is very little error in the measurement • Measurement remains constant under specific conditions
Types of Error • Random • Systematic
Effect of Unreliable Measures • Meaningless results • Inappropriate conclusions
Test-Retest Reliability • Equipment reliability • Intertester reliability • Intratester reliability
Interclass Correlation Coefficient • Measure multiple times • Assess consistency of measure • Pearson r • -1.0 - 1.0 • -1.0 = perfect negative linear relationship • 0 = no linear relationship • 1.0 = perfect positive linear relationship
Intraclass Correlation Coefficient • ICC • Sensitive to changes in: • Calibration • Error from one test to next • Multiple tester interaction • Sources of variance • Between subjects • Between occasions • Interaction between subject and test • Error
Outcomes for the ICC • Table 9-1 • Table 9-2 • Table 9-3 • Table 9-4
ICC Calculation • Repeated measures ANOVA • ICC calculated from • BMS • TMS • EMS
Precision • Standard error of the measure • SEM • As reliability increases SEM decreases