Telephone interviews were conducted by interviewers under close supervision. All data were collected by our interviewers using a Computer Assisted Telephone Interview (CATI) system invented by the research team 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.
Telephone numbers are randomly generated using known prefixes assigned to telecommunication services providers under the Numbering Plan provided by the Office of the Communications Authority (OFCA). Invalid numbers are then eliminated according to computer and manual dialing records to produce the final sample.
The target population of this survey was Cantonese-speaking Hong Kong citizens aged 18 or above. If more than one eligible subject had been available, selection was made using the “next birthday rule” which selected the person who had his/her birthday next. The survey was conducted on 3 to 4 February 2016. A total of 504 eligible respondents were successfully interviewed. The response rate of this survey was 66.9%, and the standard sampling error for percentages based on this sample was less than 2.2 percentage points. In other words, the sampling error for all percentages using the total sample was less than plus/minus 4.5 percentage points at 95% confidence level.
To ensure representativeness of the findings, the raw data collected have been rim-weighted according to provisional figures obtained from the Census and Statistics Department regarding the gender-age distribution of the Hong Kong population in 2015 mid-year and the educational attainment (highest level attended) distribution collected in the 2011 Census. All figures are based on the weighted sample.