Mode effects on self-reported alcohol use and problem drinking: mail questionnaires and personal interviewing compared.

OBJECTIVE: Much attention is paid to the influence of different data collection methods on the quality of self-reported drinking behavior estimates. Thus far, however, the findings show inconsistencies. Therefore, a comprehensive study was conducted to compare data on alcohol use and alcohol-related problems obtained by mail survey and personal interviews.
METHOD: A general population survey on alcohol was conducted among a random sample of 8,000 Dutch inhabitants of Rotterdam aged 16 to 69. A small sample (n = 500) of the total sample (N = 8,000) was personally interviewed and the others (n = 7,500) received a mailed questionnaire. The response rate was 44% (N = 3,537). Respondents of the mail survey and personal interviews are compared on overall response rate, item-nonresponse rate, background factors, self-reported alcohol use, alcohol-related problems and problem drinking.
RESULTS: No notable differences in self-reported alcohol use, alcohol-related problems or problem drinking were found by data collection mode. This holds for both the total general population and for men and women separately. The overall response rate was somewhat higher for the personal interviews. No important significant differences were found in item nonresponse or background factors.
CONCLUSIONS: The absence of notable differences in estimated self-reported drinking behavior by mail survey and personal interviews indicates that both data collection methods yield comparable results. This is true for both the total population and for men and women separately.