Supplementing CAPI with CATI in a nationally representative

Health Survey – effect on non-response

Michael Davidsen, Ola Ekholm

Copenhagen, Denmark

Plan

• The Danish Health and Morbidity Programme

• Design of the 2005 survey

• Response rate and CATI supplement

• Interpretation problems

• Comparisons of groups

• Discussion and conclusion

The Danish Health and Morbidity Survey Programme

• Nationally representative health interview surveys of adult (age 16+) Danes

• Questions on health, symptoms, illness, ilness behaviour, life style, use of health care and much more (www.si.folkesundhed/susy)

• General surveys conducted 1987, 1994, 2000 and 2005

The survey 2005

• Based on a random sample from the Danish Civil Person Register

• Data collection from May 1. 2005 – February 17. 2006 (293 days)

• Initially only interview by CAPI

• SFI-SURVEY responsible for interviews

Invitation and interview

• Written invitation, letter of introduction

• Interviewer send letter and establish contact

• Interview in the home of the respondent

• Interviewer require more persons to interview.

Sample

• Strata defined by 5 Danish regions• 3.000 interviews with response rate 70%• Two subsamples:

1. a re-re-interview of persons invited in 1994 and supplemented twice by young persons2. a random sample ensuring adequate regional sizes

Demands

• Overall response rates: 70%

• Regional response rates: 70%, capital 64%

• 21,832 person invited

• 4,688 capital; 4,286 other regions

Response ratedevelopment

Rregional response rates December 8. 2005

Region InterviewsResponse

rate (%)1 2371 50.62 2276 53.13 2806 65.54 2652 61.95 2700 63.0

Total 12805 58.7

CATI supplement

• Telephone contact to ’soft’ refuser, not met and out of town endorsed

• Only 3 regions

• Only by few ’super-interviewers’

• January and February 2006

• Same questionairre as with CAPI

CATI supplement

• Based on a pilot study of 40 persons with positive response rate.

• Information on ’soft refusers’ not available

• CATI response rate cannot be calculated

• Estimate based on pilot and information from SFI-SURVEY: 20%

Response rate final sample

Result of CATI supplement

Response December 8. CAPI CATI sup

Non-response n

Refused 2.1 7.6 90.3 4912Out of town 2.0 12.8 85.1 148

Not met 3.2 13.8 83.0 814Not contacted 42.6 6.0 51.4 2030

Other 6.7 5.7 87.6 1123Total 11.9 7.6 80.5 9027

Reginal response rate in sample

Region n % n % n %1 2731 58.3 192 4.1 2923 62.42 2499 58.3 319 7.4 2818 65.73 3077 71.8 12 0.3 3089 72.14 2776 64.8 98 2.3 2874 67.15 2792 65.1 70 1.6 2862 66.8

Total 13875 63.6 691 3.2 14566 66.7

CAPI InterviewCATI sup

Distribution according to interview status

% CAPI CATI sup Non-resp.SexMen 48.3 51.3 50.5

Women 51.7 48.7 49.5Age

16-24 9.5 14.1 10.825-44 33.2 34.6 31.345-66 39.3 35.5 36.7

67- 17.9 15.8 21.1Marital status

Widow 7.3 7.5 9.7Divorced 8.7 9.3 10.7Married 55.7 45.7 44.0

Unmarried 28.3 37.6 35.6

Effect of interview mode on selected health indicators

Age-standardised prevalence

CAPI CATI supp.

Total

Self-rated healthVery good/good 79.0 74.7 78.8

Bad/very bad 5.8 6.6 5.8

BMIObese 11.8 12.1 11.8

Alcohol consump.Abstainer 22.6 31.2 23.0

Above recommended 14.5 9.7 14.2

Discussion and conclusion I

• CATI supplement designed to improve response rate

• Reasonable success late in data collection

• Some conflicting interests when data collection company has interest in improving response rate

Discussion and conclusion II

• CATI seems to ’catch’ young, men and unmarried