Reliability and Validity of a test are the two important characteristics of a research tool. These two terms are mainly concerned with test and questionnaire. The most efficient way to understand any test is to examine how the test is constructed and how it is administered to the subject of the study population. A standardized procedure should be followed while administering the test. The evaluation of the test is primarily done by estimating the Reliability and Validity of the test items with the help of Correlation Coefficient which are quantified into numerical scores.
Reliability refers to the consistency of measurements of the test. It is used as the index of the chance of getting the same results when the test is repeated on different occasion with the same subjects. Validity of a test is primarily concerned with the extent to which the test measure what is intended to measure. It is determined by estimating the Correlation Coefficient between the test scores and some criterion. Validity is an important component of having a reliable estimate of the test scores. It is therefore necessary to decide before administering any test about the purpose, the content and the characteristics of the subjects for whom the test is intended to measure.