Sampling in educat ional research is generally conducted in order to permit the det ai led study of part, rather than the whole, of a popu lation. The information derived from the resulting sa mple is customarily employed to develop usefu l genera liz ations about the popu lation. These genera lizations may be in the form of estimates of one or more characteristics associated w ith the population, or they may be concerned with estimates of the strength of relation ships between characteristics wit hin the populat ion.