Contact informationBack

Date of survey	:	14-22 January 2009
Survey method	:	Telephone survey with interviewers
Target population	:	Cantonese-speaking population of Hong Kong of age 15 or above
Sampling method	:	The contacts were first drawn randomly from the residential telephone directories as "seed numbers", from which another set of numbers was generated by computer to produce the final telephone sample. When contacts were successfully established with a target household, one target respondent was selected using the "next birthday rule". If the selected subject was aged below 18, the interviewer first introduced the survey to his/her parent or guardian and sought his/her consent before interviewing the subject.
Sample size	:	1,531 successful cases
Overall Response rate	:	64.3%
Std. sampling error	:	Less than 1.3%. In other words, the sampling error for all percentages was less than plus/minus 2.6% at 95% confidence level.

Table 1 Breakdown of contact information of the survey

	Frequency	Percentage
Respondents' ineligibility confirmed	9,129	43.2%
Fax/ data line	982	4.6%
Invalid number	6,473	30.6%
Call-forwarding/ mobile/ pager number	236	1.1%
Non-residential number	1,159	5.5%
Special technological difficulties	67	0.3%
No eligible respondents	212	1.0%

Respondents' ineligibility not confirmed	5,282	25.0%
Line busy	503	2.4%
No answer	3,389	16.0%
Answering device	89	0.4%
Call-blocking	76	0.4%
Language problem	360	1.7%
Interview terminated before the screening question	748	3.5%
Others	117	0.6%

Respondents' eligibility confirmed, but failed to complete the interview	5,181	24.5%
Household-level refusal	6	0.0%
Known respondent refusal	16	0.1%
Appointment date beyond the end of the fieldwork period	4,868	23.0%
Partial interview	81	0.4%
Miscellaneous	210	1.0%

Successful cases	1,531	7.2%

Total	21,123	100.0%

Table 2 Calculation of effective response rate

Overall Response rate
= [ Successful cases / (Successful cases + Partial interview* + Refusal cases by eligible respondents^ ) ]
= [ 1,531 / ( 1,531 + (81+748) + (6+16)) ]
= 64.3%

* Including "partial interview" and "Interview terminated before the screening question"
^ Including "household-level refusal" and "known respondent refusal"