This was a random telephone survey conducted by interviewers under close supervision. 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 Hong Kong residents aged 18 or above who spoke Cantonese. When telephone contact was successfully established with a target household, one person of age 18 or above who spoke Cantonese was selected. If more than one subject had been available, selection was made using the "next birthday rule" which selected the person who had his/her birthday next.
Telephone interviews were conducted during the period of 3 to 14 March, 2013. A total of 1,039 Hong Kong residents of age 18 or above were successfully interviewed. The overall response rate of this survey was 66.9%, and the standard sampling error for percentages based on this sample was less than 1.6 percentage points. In other words, the sampling error for all percentages using the total sample was less than plus/minus 3.1 percentage points at 95% confidence level.