Table 2

Outcome measures and comparison of percentage response rates from surveys 1, 2 and 3 calculated as per AAPOR definitions [9]

Survey 1

Survey 2

Survey 3


n

% of numbers dialled

n

% of numbers dialled

n

% of numbers dialled

A

Eligible*

11,782

52.9%

3,425

50.2%

10,401

31.8%

Completed interviews

9,903

44.5%

1,538

22.3%

4,216

12.9%

Refusals

1,815

8.1%

1,015

14.9%

2,472

7.5%

Non-contact

64

0.29%

826

12.1%

3,709

21.0%

B

Ineligible**

5,378

24.1%

1,351

19.8%

1,821

5.5%

C

Eligibility unknown †

5,121

23.0%

2,042

30.0%

5,422

62.7%

Total telephone numbers dialled‡

22,281

(100%)

6,818

(100%)

17,644

(100%)

Responserate (percentage)

58.6%

28.1%

17.7%

Contactrate (percentage)

69.7%

47.5%

32%

Co-operation rate (percentage)

84.1%

45.5%

40.5%


* Eligible calls included cases where an interview was completed, refusal occurred, non-contact at a residential household (e.g. residential answering machine) or where respondents were unable to complete the interview due to language difficulties or disability.

** Ineligible calls included non-residential numbers (such as business or fax lines) and telephone numbers which were invalid (both confirmed and suspected).

† Calls where eligibility was unknown were recorded separately. These were mostly calls which rang, but were not answered, rang out or were engaged, or where phone problems occurred.

‡ This differs from contact attempts (Table 1) as it excludes those numbers that were redialled. In survey 1 all telephone numbers generated were used. In surveys 2 and 3, sampling of extracted or generated numbers respectively was undertaken so only a proportion were used for dialling.

Response Rate (minimum response rate) is the number of complete interviews divided by the number of interviews (complete plus partial) plus the number of non-interviews (refusals and break-off plus non-contacts plus others) plus all cases of unknown eligibility (unknown if housing unit, plus unknown, other).

Contact Rate measures the proportion of all cases in which some responsible member of the housing unit was reached by the survey.

Co-operation Rate is the proportion of all cases interviewed of all eligible units ever contacted.

Co-operation rate = C/C [C + R +O]* 100

Where C = completed interview

R = Refusal

O = other (not completed because of language barrier or sickness/disability.

9,903/[9,903 + 1,815 + 64]*100

= 84.1%

Boland et al. BMC Public Health 2006 6:208   doi:10.1186/1471-2458-6-208

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