Point –biserial technique to measure the validity of knowledge test

Behavioral scientists often restrict to measure the tests’ validity with the help of content validity or some other convenient or easiest techniques which are not statistical. Therefore, we can not rely more on these techniques. The term validity means truthfulness. Lindquist (1951) defined “validity of a test as the accuracy with which it measures that is intended to be measured.” One common technique used to measure item validity of test is the point -biserial correlation (rpb). The “pt bis”, as it is sometimes called is the correlation between an item score (1/0) and the total score on a test (Downee and Heath, 1970). The present paper attempts to measure the validity of a knowledge test with the help of pointbiserial correlation coefficient. Point-biserial technique is more powerful than that of biserial technique. The present paper is based on original data. Behavioural scientists and students are advised to use this mathematical technique which proves to be more authentic.