PS295 Lecture : Reliability and Validity of Measures.docx
Document Summary
Two characteristics a measure has to have is reliability and validity. Reliability refers to the consistency or dependability of a measure how consistently a measure assigns the same score to the same observation. Every score on a measure consists of two components. Observed score = true score + measurement error the two components. True score: the score if the measure were perfect. Error: the result of factors that distort the observed score, so that it differs from the true score. Sources of measurement error any factor that will influence where a person scored on the measure that isn"t reflecting their true score/true ability. Total variance in a set of scores = variance due to true scores + variance due to measurement error. Reliability = true score variance / total variance. Reliability is the proportion of the total variance in a set of scores that is associated with participants" true scores.
