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 survey was conducted during the period of December 5 to 10, 2012. 515 respondents were successfully interviewed. The effective response rate was 69.2%, 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.