The target population of this survey was Cantonese-speaking population of Hong Kong of age 18 or above. To minimize sampling bias, the following sampling technique was adopted:

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.

When telephone contact was successfully established with a target household, one person of age 18 or above was selected. If more than one qualified 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. Please refer to Appendix 1 for the demographic profile of the respondents.

Telephone interviews were carried out between 25 May and 15 June 2009. Data were collected by interviewers using a Computer Assisted Telephone Interviews (CATI) system under close supervision.

As shown from the detailed breakdown of the contact information, among the 15,402 telephone numbers sampled for the survey, 6,869 were confirmed ineligible, among them 666 were fax or data lines, 5,198 were invalid telephone numbers, 171 were call-forwarding numbers, while another 755 were non-residential numbers. Besides, 45 of them were invalidated due to special technological circumstances, while 34 cases were voided because no eligible respondents were available at the numbers provided.

Meanwhile, a total of 3,839 telephone numbers were invalidated since the research team could not confirm their eligibility. Among them 235 were busy lines, 2,651 were no-answer calls, 77 cases were diverted to answering devices while 54 were blocked. In addition, 222 cases were treated as ineligible because of language problems, 559 interviews were terminated before the screening question, while 41 cases were voided for other problems.

To sum up, a total of 1,201 Hong Kong residents of age 18 or above were successfully interviewed in this survey. The overall response rate was 65. 2% as shown in the following calculation. The standard error due to sampling was no more than 1.4 percentage points.

The 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 at the end of 2008. All analyses in this report are based on the weighted data.

Statistical tests of 「difference-of-proportions」 and 「difference-of-means」 have been employed whenever applicable, in order to check for significant changes. Figures marked with single asterisk (*) denoted statistical significance at p=0.05 level whereas those with double asterisks (**) indicated that the variation has been tested to be statistically significant at p=0.01 level.