Probably the best way to guard against this type of bias is to obtain all criterion data before
any predictor data are released. Thus, in attempting to validate assessment center predictions,
Bray and Grant (1966) collected data at an experimental assessment center, but these data had no
bearing on subsequent promotion decisions. Eight years later the predictions were validated
against a criterion of "promoted versus not promoted into middle management." By carefully
shielding the predictor information from those who had responsibility for making promotion
decisions, a much "cleaner" validity estimate was obtained.