Pairwise deletion

One of the options or methods available to a researcher in treating the missing responses from the filled up questionnaires. In this option, instead of deleting all cases with any missing number, the researcher uses only the cases or respondents with complete responses for each calculation. As a result, different calculations in an analysis may be based on different sample sizes. This procedure may be appropriate when (1) the sample size is large, (2) there are few missing responses, and (3) the variables are not highly related. Yet, this procedure can produce results that are unappealing or even infeasible.