Evaluation of a Mailed Planning Survey

Non–response bias in alcohol and drug population surveys

“…Another study comparing early respondents with late respondents showed significant differences between early and late responses in age, sex, occupation, but not in education and location of the household [34]. Waltz and Grecco found significant differences between early and late respondents in sex, education and occupation, but not in age, city of residence and marital status [35]. These conflicting results might suggest that nonresponse biases exist in some surveys, such as the 2004 CAS, but the extent of this bias might vary according to subject matter of the investigation.…”