Research DesignBack
This was a random telephone survey conducted by interviewers under close supervision using the Web-based Computer Assisted Telephone Interview (Web-CATI) system, which allowed real-time data capture and consolidation. 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. The target population of this survey was the Cantonese-speaking local population aged 15 or above and have shopped in supermarkets in the past month. When telephone contact was successfully established with a target household, one target respondent 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.
This survey was conducted during the period of April 2009 to January 2010 in three stages. Sample size of each stage was 1,000 or more successful interviews with Hong Kong residents. Please refer to the table below.
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. Please refer to each table in Appendix 2. However, it is noteworthy that whether numerical changes are statistically valid does not equal to the actual usage and meaning of such changes. | ||||||||||||||||||||||||
