Data from an epidemiologic study of schizophrenia were used to determine how many subjects in the large sample pool met eligibility criteria for family study. Of 549 patients with interview data only 29.1% were eligible. Eligible were compared with ineligible schizophrenic patients on 15 variables likely to influence family interaction patterns; the small group of male patients who actually cooperated in the Family Study were compared on the same variables with those who refused to participate. On nine variables the groups were similar, but they differed on six. Eligible and cooperating patients were of higher socioeconomic status and earlier birth order; they were younger when interviewed and when admitted to the hospital; and were more likely to have been diagnosed acute rather than paranoid or chronic schizophrenic.
Wild CM, Shapiro LN, Abelin T. Sampling Issues in Family Studies of Schizophrenia. Arch Gen Psychiatry. 1974;30(2):211-215. doi:10.1001/archpsyc.1974.01760080067011