Principles and methods of validity and reliability testing of questionnaires used in social and health science researches.

The importance of measuring the accuracy and consistency of research instruments (especially questionnaires) known as validity and reliability, respectively, have been documented in several studies, but their measure is not commonly carried out among health and social science researchers in developing countries. This has been linked to the dearth of knowledge of these tests. This is a review article which comprehensively explores and describes the validity and reliability of a research instrument (with special reference to questionnaire). It further discusses various forms of validity and reliability tests with concise examples and finally explains various methods of analysing these tests with scientific principles guiding such analysis.