The purpose of this study was to compare response distributions in health surveys for two inteniew modes: face-to-face household interviews and telephone interviews. There were two samples of the Perth metropolitan general population aged 16 to 69 years: a face-to-face household sample (n= 1000) and a telephone sample (n= 222). The samples were generated by probability-based methods commonly used by commercial market research organisations. The surveys occurred in August-September 1992 as part of a larger statewide survey component of a three-year evaluation of the M'estern Australian Health Promotion Foundation. Respondents were drawn from a two-stage cluster sample based on private dwellings for personal interviews, and from randomly selected listed and unlisted private numbers for telephone interviews. Although the samples did not differ significantly on a number of variables, the telephone sample was significantly higher in residential social status; there was significantly lower reporting of smoking and lower unsafe alcohol consumption in the telephone sample; significantly higher proportions of. the telephone sample were in Prochaska's ‘action’ stage of change for several health behaviours; and there was significantly greater recall of health messages in the telephone sample. Health researchers should treat comparisons between different survey modes with caution, and should be aware that campaign evaluations using telephone surveys and household surveys may yield substantially different results.
