one of the two parties to call a third party without hanging up and allowing all three parties to have simultaneous phone conversation) after the briefing. The interviewer left the line after the connection was made. Respondents then completed the computerised questionnaire by keying in their responses after listening to the prerecorded questions. The "dot line" telephone number was not released to the respondents. The service has often been used by TV stations for public opinion polling and is widely known to the public. All respondents were guaranteed that their telephone number would not be recorded. Anonymity and confidentiality were therefore enhanced. The TICQM has been employed in a number of local studies. 9, 13 -- 15 A literature search showed that this method had been original. Out of all telephone calls made, 23.8% were non-contacts (after three attempts) and about 20% were non-households. Among those contacted households (these households with someone answering the call), 40% were invalid households (without or could not contact an eligible respondent), 29% refused to join the study, and 31% completed the study. An overall response rate, defined as the number of respondents completing the study divided by the number of completed interviews plus refusals, was 51.6%. This is comparable with other telephone surveys conducted in Hong Kong. 9, 14, 16 -- 18 On average, it took the TICQM respondents about 7 -- 8 minutes and the TIM respondents about 5 -- 6 minutes to complete part II of the questionnaire. Measurements Two structured questionnaires,