The effects of using answer sheets on reported drug use and data quality in a classroom survey A cluster-randomized study.
We compare self-reported prevalence of drug use and indicators of data quality from two different response modes (with and without an independent answer sheet for recording responses) in a survey conducted in 2015 among secondary school students. Stratified cluster-randomized study conducted among students in grades 8-12 from public, private and subsidized schools in Chile (N2317 students in 122 classes). Measurements included were percentage reporting substance use (tobacco, alcohol, marijuana, cocaine, ecstasy) number of inconsistent responses number of item nonresponses percentage of extreme reports of drug use percentage reporting using the nonexistent drug, relevón and completion times. Compared with those who responded directly in the questionnaire booklet, students who used a separate answer sheet took 17.6 more minutes (95% confidence interval CI 14.4-20.8) to complete the survey and had on average 1.5 more inconsistent responses (95%CI 0.91-2.14). The prevalence and variance of drug use was higher among those who used an answer sheet for all substances except tobacco the prevalence ratio (PR) of reported substance use for low-prevalence substances during the past year were cocaine PR2.5 (95%CI 1.6-4.1) ecstasy PR5.0 (95%CI 2.4-10.5) relevón PR4.8 (95%CI 2.5-9.3). Using an answer sheet for a self-administered paper-and-pencil survey of drug use among students result in lower quality data and higher reports of drug use. International comparison of adolescent drug use from school-based surveys should be done with caution. The relative ranking of a country could be misleading if different mode of recording answers are used.