A Comparison of Methods for Treating Incomplete Data in Selection Research

Data were simulated to conform to covariance patterns taken from the personnel selection literature. Two, six, and ten percent of the values were deleted from one of three predictor variables in sample sizes of 50, 100 and 200. Incomplete data matrices were treated by four methods: (a) elimination of cases with incomplete data records; (b) substitution of missing values with the variable mean; (c) replacement of missing values with an estimate obtained from simple regression; and (d) replacement of missing values with an estimate derived from iterated multiple regression. The treated data matrices were subjected to multiple regression analyses, and the resulting regression equations were compared to the equations obtained from the original, complete data. The two regression based estimation procedures provided the most accurate regression equations, followed by the method of inserting means. Discarding cases with incomplete records was the least accurate method. Although the results supported the practice of using covariate information to estimate missing data, the increases in accuracy were minimal under the conditions investigated.