Correspondence Address: Oladimeji Akeem Bolarinwa From the Department of Epidemiology and Community Health, University of Ilorin and University of Ilorin Teaching Hospital, Ilorin Nigeria Source of Support: None, Conflict of Interest: None 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.From the author's personal observation among researchers in developing countries, most students and young researchers are not able to distinguish validity from reliability.Likewise, they do not have the prerequisite to understand the principles that underline validity and reliability testing of a research measurement tool.
For example, a researcher is interested in evaluating employees' attitudes towards a training program on hazard prevention within an organisation.
It could be adapted from an already tested one or could be developed as a new data tool specific to measure or quantify a particular attribute.
These conditions therefore warrant the need to test validity and reliability of questionnaire.
Internal validity refers to how accurately the measures obtained from the research was actually quantifying what it was designed to measure whereas external validity refers to how accurately the measures obtained from the study sample described the reference population from which the study sample was drawn. Postal and electronic questionnaires are known as self-completion questionnaires, i.e., respondents complete them by themselves in their own time.
Structured questionnaires are usually associated with quantitative research, which means research that is concerned with numbers (how many? F2F and telephone questionnaires are used by interviewers to ask a standard set of questions and record the responses that people give to them.