Telephone interviews were conducted by interviewers under close supervision. All data were collected by our interviewers using a Computer Assisted Telephone Interview (CATI) system which allowed real-time data capture and consolidation. To ensure data quality, on top of on-site supervision, voice recording, screen capturing and camera surveillance were used to monitor the interviewers' performance.
The target population of this survey is Hong Kong residents aged 18 to 64 who speak Cantonese. If more than one subject had been available, the one who had his/her birthday next was selected.
The survey was conducted during the period of October 8 to 10, 2012. 523 respondents were successfully interviewed. The effective response rate was 68.4%, and the standard sampling error for percentages based on this sample was less than 2.2 percentage points. In other words, the maximum sampling error for percentages was less than plus/minus 4.4 percentage points at 95% confidence level.