These validity tests are categorised into two broad components namely internal and external validities. Several varieties have been described, including face validity, construct validity, content validity and criterion validity (which could be concurrent and predictive validity). Validity expresses the degree to which a measurement measures what it purports to measure. This is with a view to critically review current principles and methods of reliability and validity tests as they are applicable to questionnaire use in social and health researches.
To achieve the stated goal, the author reviewed currents articles (both print and online), scientific textbooks, lecture notes/presentations and health programme papers. This article therefore sets out to review the principles and methods of validity and reliability measurement tools used in social and health science researches. Likewise, they do not have the prerequisite to understand the principles that underline validity and reliability testing of a research measurement tool. From the author's personal observation among researchers in developing countries, most students and young researchers are not able to distinguish validity from reliability. This has been adduced to the dearth of skills and knowledge of validity and reliability test analysis among social and health science researchers. As simple as this may seems, it is often omitted or just mentioned passively in the research proposal or report. The researchers always wish to know if the measurement tool employed actually measures the intended research concept or construct (is it valid? or true measures?) or if the measurement tools used to quantify the variables provide stable or consistent responses (is it reliable? or repeatable?). One of the most common tasks often encountered in social science research is ascertaining the validity and reliability of a measurement tool. The various measurements will ultimately require measurement tools through which the values will be captured. These can be observational, self-report, interview and record review. In addition, the inferences made will depend on the type of measurement. However, these quantification will come in the different forms of inference. The different measurements in social science research require quantification of abstracts, intangible and construct that may not be observable. Principles and methods of validity and reliability testing of questionnaires used in social and health science researches. Keywords: Questionnaire, reliability, social and health, validity 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. This is a review article which comprehensively explores and describes the validity and reliability of a research instrument (with special reference to questionnaire). This has been linked to the dearth of knowledge of these tests.
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.