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This was a random telephone survey conducted by telephone interviewers under close supervision. To minimize sampling bias, telephone numbers were first drawn randomly from the residential telephone directories as 「seed numbers」, from which another set of numbers was generated using the 「plus/minus one/two」 method, in order to capture the unlisted numbers. Duplicated numbers were then filtered, and the remaining numbers were mixed in random order to produce the final telephone sample. Target respondents of the study were Cantonese-speaking population of Hong Kong of age 16 or above. When telephone contact was successfully established with a target household, one qualified person 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 from all those present.

The fieldwork was conducted during the period of August 14 to 26, 2008. A total of 515 Hong Kong citizens who fulfilled the abovementioned criteria were successfully interviewed. The overall response rate of the survey was 65.3% (Table 1 and 2, Appendix I), and the sampling error for percentages was less than 2.2%. In other words, the sampling error for all percentages was less than plus/minus 4.4% at 95% confidence level.

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.

To ensure representativeness of the findings, the raw data collected have been adjusted according to provisional figures obtained from the Census and Statistics Department regarding the gender-age distribution of the Hong Kong population in 2007 year-end. All analyses in this report are based on the weighted sample.