Contact information
 

  Date of survey : May 7 to 15 and June 2 to 13, 2008
  Survey method : Random telephone survey conducted by real interviewers
  Target population : Cantonese-speaking population of Hong Kong who fulfilled either one of the following criteria: 1) parents aged 18-year or above with at least one child aged 17-year or below; 2) young adults aged between 18 and 34-year with no children; and 3) children aged between 9 and 17-year.
  Sampling method :
The contacts 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.
  Sample size : 1,516 successful cases, with 506 parents, 506 young adults and 504 children
  Overall Response rate :

Parents: 77.8%
Young adults: 77.9%
Children: 79.3%

  Std. sampling error : Less than 2.2 percentage points. In other words, the sampling error for all percentages was less than plus/minus 4.5percentage points at 95% confidence level.

Table 1 Breakdown of contact information of the survey (Parents)

 

Frequency

Percentage

Respondents' ineligibility confirmed

 10,547

 50.7%

Fax/ data line

943

4.5%

Invalid number

6,242

30.0%

Call-forwarding/ mobile/ pager number

160

0.8%

Non-residential number

1,104

5.3%

Special technological difficulties

99

0.5%

No eligible respondents

1,999

9.6%

 

 

 

Respondents' ineligibility not confirmed

 5,263

 25.3%

Line busy

420

2.0%

No answer

3,614

17.4%

Answering device

107

0.5%

Call-blocking

77

0.4%

Language problem

360

1.7%

Interview terminated before the screening question

523

2.5%

Others

162

0.8%

 

 

 

Respondents' eligibility confirmed, but failed to complete the interview

4,468 

21.5% 

Household-level refusal

13

0.1%

Known respondent refusal

8

0.0%

Appointment date beyond the end of the fieldwork period

4,112

19.8%

Partial interview

12

0.1%

Miscellaneous

323

1.6%

 

 

 

Successful cases

 506

2.4% 

 

 

 

Total

 20,784

100.0% 


Table 2 Calculation of effective response rate (Parents)

   Effective response rate
= [ Successful cases / (Successful cases + Partial interview + Refusal cases by eligible respondents* + Refusal cases by prorated-eligible respondents^) ]
= [ 506 / ( 506+ 12 + 13 + 8 + 523[(506 + 12 + 13+8) / (506 + 12 + 13 + 8+1999)]^) ]
= 77.8%
* Including "household-level refusal" and "known respondent refusal"
^ Figure obtained by prorata



Table 3 Breakdown of contact information of the survey (Young adults)
 

Frequency

Percentage

Respondents' ineligibility confirmed

10,549

50.8%

Fax/ data line

943

4.5%

Invalid number

6,242

30.0%

Call-forwarding/ mobile/ pager number

160

0.8%

Non-residential number

1,104

5.3%

Special technological difficulties

99

0.5%

No eligible respondents

2,001

9.6%

 

 

 

Respondents' ineligibility not confirmed

5,261

25.3%

Line busy

420

2.0%

No answer

3,613

17.4%

Answering device

107

0.5%

Call-blocking

77

0.4%

Language problem

360

1.7%

Interview terminated before the screening question

522

2.5%

Others

162

0.8%

 

 

 

Respondents' eligibility confirmed, but failed to complete the interview

4,468

21.5%

Household-level refusal

13

0.1%

Known respondent refusal

8

0.0%

Appointment date beyond the end of the fieldwork period

4,112

19.8%

Partial interview

12

0.1%

Miscellaneous

323

1.6%

 

 

 

Successful cases

506

2.4%

 

 

 

Total

20,784

100.0%


Table 4 Calculation of effective response rate (Young adults)

   Effective response rate
= [ Successful cases / (Successful cases + Partial interview + Refusal cases by eligible respondents* + Refusal cases by prorated-eligible respondents^) ]
= [ 506 / ( 506+12+13+8 + 522[(506+12+13+8) / (506+12+13+8+2001)]^ ) ]
= 77.9%
* Including "household-level refusal" and "known respondent refusal"
^ Figure obtained by prorata



Table 5 Breakdown of contact information of the survey (Children)
 

Frequency

Percentage

Respondents' ineligibility confirmed

16,951

53.7%

Fax/ data line

1,310

4.2%

Invalid number

8,644

27.4%

Call-forwarding/ mobile/ pager number

222

0.7%

Non-residential number

1,559

4.9%

Special technological difficulties

155

0.5%

No eligible respondents

5,061

16.0%

 

 

 

Respondents' ineligibility not confirmed

7,550

23.9%

Line busy

589

1.9%

No answer

5,303

16.8%

Answering device

134

0.4%

Call-blocking

110

0.3%

Language problem

462

1.5%

Interview terminated before the screening question

683

2.2%

Others

269

0.9%

 

 

 

Respondents' eligibility confirmed, but failed to complete the interview

6,540

20.7%

Household-level refusal

27

0.1%

Known respondent refusal

22

0.1%

Appointment date beyond the end of the fieldwork period

5,898

18.7%

Partial interview

14

0.0%

Miscellaneous

579

1.8%

 

 

 

Successful cases

504

1.6%

 

 

 

Total

31,545

100.0%


Table 6 Calculation of effective response rate (Children)

   Effective response rate
= [ Successful cases / (Successful cases + Partial interview + Refusal cases by eligible respondents* + Refusal cases by prorated-eligible respondents^) ]
= [ 504 / ( 504+14 +27+22+683[(504+14+27+22) / (504+14+27+22+5061)]^ ) ]
= 79.3%
* Including "household-level refusal" and "known respondent refusal"
^ Figure obtained by prorata




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