Estimates of Potential Bias in Telephone Substance Abuse Surveys Due to Exclusion of Households without Telephones

This article reports estimates of the bias that may result in telephone substance abuse surveys because of the noncoverage of households without telephones. The study analyzed 1995–1998 data from the face-to-face National Household Survey on Drug Abuse. Residents of households with telephones reported less drug use, less dependence on drugs and alcohol, but more alcohol use than residents of households without telephones. The resulting percentage differences between respondents with telephones and respondents in all households averaged one tenth of a percent (0.1%), and ratios of percentage estimates for all households to households with telephones averaged 1.04. The bias varied by substance, time frame, use versus dependence, and demographic characteristics. For example, use of marijuana ever had less bias than past year cocaine dependence. American Indians/Alaska Natives had the greatest amount of potential bias. For most populations and policy objectives, it may not be worth the added expense of conducting supplementary face-to-face interviews with residents of households without telephones in order to eliminate the bias.