Reliability and validity testing of questionnaire or scale

readibilty validating meaurement Reliability in layperson language means precision or reproducibility. If a new scale or questionnaire instrument is developed, its reproducibility or precision can be estimated by inter-rater and test-retest correlation coefficients as well as internal consistency measure of Cronabach alpha coefficient.

Validity testing implies accuracy of a scale in capturing its intended target. Validity evaluation involves face validity (items understandable by study subjects), content validity (items qualified by various experts), construct validity (by factor analysis), concurrent validity (testing associations or correlation against gold standard) and predictive validity (by regression modeling).