validity and reliability of research instrument

If the results are different, then the measurement is unreliable. A reliable measurement is one that if repeated a second time will give the same results as it did the first time. Whenever an investigator measures a variable, he or she wants to be sure that the measurement provides dependable and consistent results. Reliability refers to the consistence, stability, or dependability of the data. However, when handling qualitative information such as feelings, likes, dislikes, opinions etc, validity is more difficult to determine. For example in growth monitoring, the height and weight of a child is easy to determine. Validity of an instrument is easy to determine if one is dealing with information that can be quantified. But if is reliable, it may or may not be valid. If a measurement is valid, it is also reliable. Data need not only to be reliable but also true and accurate. This refers to the extent to which a measurement does what it supposed to do. The reliability of the findings, conclusions and recommendations arrived at in any study largely depends on the validity, and reliability of the methods and instruments used in data collection. This section explains the technical meaning of these two concepts. This then requires that the tool for the collection of data is valid and reliable.

View Full Text.In research the concern of an investigator is how to minimize possible errors and bias by maximizing the reliability and validity of data. In this learning paper, main types of validity namely face validity, content validity, construct validity, criterion validity and reliability are discussed. Validity basically means “measure what is intended to be measured” (Field, 2005). Validity explains how well the collected data covers the actual area of investigation (Ghauri and Gronhaug, 2005). This learning paper explores and describes the validity and reliability of a questionnaire/survey and also discusses various forms of validity and reliability tests. Often new researchers are confused with selection and conducting of proper validity type to test their research instrument (questionnaire/survey).

Thus the accuracy and consistency of survey/questionnaire forms a significant aspect of research methodology which are known as validity and reliability. The main objective of questionnaire in research is to obtain relevant information in most reliable and valid manner. Questionnaire is one of the most widely used tools to collect data in especially social science research.

Validity and reliability of research instrument