Background
Method
Target population
Survey protocol
Round | Incentive for completing the survey | Survey length | Number of follow-up waves | Incentive for participating in field study | Addressee | % deliverable |
---|---|---|---|---|---|---|
1 | Gift card | Long | 0 | $100 | “Current Resident” | 91.3 |
2 | Gift card | Long | 0 | $100 | “Current Resident” | 92.9 |
3 | Gift card | Long | 0 | $100 | Personalized | 91.7 |
4 | Gift card | Long | 0 | $100 | Personalized | 88.8 |
5 | Gift card | Long | 0a | $100 | Personalized | 91.3 |
6 | $2 cash | Long | 3 | $150 | Personalized | 88.3 |
7 | $2 cash | Long | 3 | $150 | Personalized | 89.6 |
8 | $2 cash | Medium | 3 | $150 | Personalized | 87.5 |
9 | $2 cash | Short | 3 | $150 | Personalized | 86.3 |
10 | $2 cash | Long | 3 | $200 | Personalized | 84.6 |
11 | $2 cash | Long | 0 | $200 | Personalized | 91.3 |
12 | $2 cash | Long | 3 | $200 | Personalized | 85.0 |
13 | $2 cash | Long | 3 | $200 | Personalized | 86.3 |
14 | $2 cash | Long | 2 | $200 | Personalized | 85.4 |
15 | $2 cash | Long | 2 | $200 | Personalized | 84.2 |
16 | $2 cash | Long | 2 | $200 | Personalized | 83.8 |
17 | $2 cash | Long | 2 | $200 | Personalized | 82.1 |
Analysis
Results
Delivery rates
Survey completion
Model and test relative to intercept-only model | Variable | Fixed effects | Variable level | Completing survey | ||||
---|---|---|---|---|---|---|---|---|
df | Wald χ2 | p-value | p-value | OR | 95% CI | |||
Model 1 χ2(6, n = 3576) = 158.793, p < 0.0001 | Survey incentive | 1 | 11.599 | < 0.001 | Gift card | Ref | ||
$2 | < 0.001 | 2.792 | 1.546–5.041 | |||||
Survey length | 2 | 2.569 | 0.277 | Short | Ref | |||
Medium | 0.752 | 0.927 | 0.579–1.484 | |||||
Long | 0.139 | 0.730 | 0.482–1.107 | |||||
Follow-up waves | 2 | 9.627 | 0.008 | 0 | Ref | |||
2 | 0.114 | 1.530 | 0.903–2.591 | |||||
3 | 0.005 | 2.121 | 1.250–3.597 | |||||
Field study incentive | 1 | 0.150 | 0.699 | 150 | Ref | |||
200 | 0.699 | 0.936 | 0.671–1.306 | |||||
Model 2 χ2(11, n = 3576) = 162.574, p < 0.0001 | Survey incentive | 1 | 11.643 | < 0.001 | Gift card | Ref | ||
$2 | < 0.001 | 2.798 | 1.550–5.054 | |||||
Survey length | 2 | 2.505 | 0.286 | Short | Ref | |||
Medium | 0.759 | 0.929 | 0.580–1.488 | |||||
Long | 0.144 | 0.733 | 0.483–1.112 | |||||
Follow-up waves | 2 | 9.592 | 0.008 | 0 | Ref | |||
2 | 0.114 | 1.530 | 0.903–2.592 | |||||
3 | 0.005 | 2.120 | 1.249–3.596 | |||||
Field study incentive | 1 | 0.170 | 0.680 | 150 | Ref | |||
200 | 0.680 | 0.932 | 0.668–1.301 | |||||
Noise exposure category | 4 | 3.397 | 0.494 | < 40 | Ref | |||
40–45 | 0.562 | 0.907 | 0.651–1.263 | |||||
45–50 | 0.306 | 0.839 | 0.599–1.175 | |||||
50–55 | 0.671 | 1.073 | 0.776–1.484 | |||||
> 55 | 0.594 | 1.093 | 0.787–1.519 | |||||
Direction | 1 | 1.073 | 0.300 | West | Ref | |||
East | 0.538 | 0.936 | 0.758–1.156 |
Interest
Model and test relative to intercept-only model | Variable | Fixed effects | Variable level | Interest in field study | ||||
---|---|---|---|---|---|---|---|---|
df | Wald χ2 | p-value | p-value | OR | 95% CI | |||
Model 1 χ2(6, n = 402) = 6.885, p = 0.332 | Survey incentive | 1 | 2.106 | 0.147 | Gift card | Ref | ||
$2 | 0.147 | 0.417 | 0.128–1.359 | |||||
Survey length | 2 | 2.628 | 0.269 | Short | Ref | |||
Medium | 0.819 | 1.111 | 0.452–2.733 | |||||
Long | 0.233 | 0.621 | 0.284–1.358 | |||||
Follow-up waves | 2 | 1.735 | 0.420 | 0 | Ref | |||
2 | 0.366 | 1.595 | 0.581–4.384 | |||||
3 | 0.811 | 1.130 | 0.414–3.090 | |||||
Field study incentive | 1 | 0.001 | 0.971 | 150 | Ref | |||
200 | 0.971 | 1.011 | 0.550–1.861 | |||||
Model 2 χ2(11, n = 402) = 20.832, p = 0.035 | Survey incentive | 1 | 2.095 | 0.148 | Gift card | Ref | ||
$2 | 0.148 | 0.408 | 0.121–1.373 | |||||
Survey length | 2 | 2.854 | 0.240 | Short | Ref | |||
Medium | 0.753 | 1.158 | 0.463–2.899 | |||||
Long | 0.234 | 0.615 | 0.277–1.369 | |||||
Follow-up waves | 2 | 1.564 | 0.457 | 0 | Ref | |||
2 | 0.422 | 1.529 | 0.543–4.310 | |||||
3 | 0.876 | 1.086 | 0.388–3.038 | |||||
Field study incentive | 1 | 0.010 | 0.921 | 150 | Ref | |||
200 | 0.921 | 0.969 | 0.519–1.808 | |||||
Noise exposure category | 4 | 10.830 | 0.029 | < 40 | Ref | |||
40–45 | 0.311 | 0.721 | 0.383–1.358 | |||||
45–50 | 0.150 | 1.619 | 0.841–3.118 | |||||
50–55 | 0.072 | 1.775 | 0.949–3.318 | |||||
> 55 | 0.171 | 1.558 | 0.826–2.940 | |||||
Direction | 1 | 2.049 | 0.152 | West | ||||
East | 0.152 | 0.738 | 0.487–1.119 | |||||
Model 3 χ2(17, n = 359) = 63.308, p < 0.0001 | Survey incentive | 1 | 3.719 | 0.054 | Gift card | Ref | ||
$2 | 0.054 | 0.245 | 0.059–1.023 | |||||
Survey length | 2 | 1.659 | 0.436 | Short | Ref | |||
Medium | 0.873 | 1.086 | 0.396–2.973 | |||||
Long | 0.330 | 0.647 | 0.270–1.553 | |||||
Follow-up waves | 2 | 1.461 | 0.482 | 0 | Ref | |||
2 | 0.228 | 2.153 | 0.619–7.489 | |||||
3 | 0.332 | 1.851 | 0.534–6.421 | |||||
Field study incentive | 1 | 0.164 | 0.685 | 150 | Ref | |||
200 | 0.685 | 1.160 | 0.565–2.381 | |||||
Noise exposure category | 4 | 8.904 | 0.064 | < 40 | Ref | |||
40–45 | 0.803 | 0.909 | 0.430–1.924 | |||||
45–50 | 0.114 | 1.846 | 0.863–3.949 | |||||
50–55 | 0.029 | 2.304 | 1.088–4.875 | |||||
> 55 | 0.132 | 1.768 | 0.842–3.713 | |||||
Direction | 1 | 0.642 | 0.423 | West | Ref | |||
East | 0. 423 | 0.823 | 0.511–1.326 | |||||
Sex | 1 | 0.961 | 0.327 | Female | Ref | |||
Male | 0. 327 | 0.774 | 0.464–1.202 | |||||
Age category | 5 | 33.150 | < 0.0001 | < 30 | Ref | |||
30–39 | 0.073 | 0.140 | 0.016–1.202 | |||||
40–49 | 0.029 | 0.094 | 0.011–0.781 | |||||
50–59 | 0.010 | 0.065 | 0.008–0.525 | |||||
60–69 | 0.001 | 0.032 | 0.004–0.257 | |||||
≥70 | < 0.001 | 0.022 | 0.003–0.183 |
Participation
Questionnaire completion and field study participation probabilities
Sample size (n) | Probability of completing survey and 95% CIs (%) | Follow-up waves | Survey length | Survey incentive |
---|---|---|---|---|
207 | 21.7 (16.6–27.9) | 3 | Short | $2 |
210 | 20.5 (15.6–26.5) | 3 | Medium | $2 |
1041 | 16.3 (14.2–18.7) | 3 | Long | $2 |
805 | 12.0 (10.0–14.5) | 2 | Long | $2 |
219 | 8.2 (5.2–12.7) | 0 | Long | $2 |
1094 | 3.1 (2.2–4.3) | 0 | Long | Gift card |
Total = 3576 |
Follow-up waves | Survey length | Field study participation amount | Sample size (n) | Probability of participating in field study (% with 95% CIs)a | Probability of participating among survey respondents (% with 95% CIs)b |
---|---|---|---|---|---|
3 | Short | $150 | 207 | 2.9 (1.3–6.3) | 13.3 (6.1–26.7) |
3 | Medium | $150 | 210 | 2.4 (1.0–5.6) | 11.6 (4.9–25.1) |
3 | Long | $150 | 427 | 2.1 (1.1–4.0) | 12.5 (6.6–22.3) |
2 | Long | $200 | 805 | 1.0 (0.5–2.0) | 8.2 (4.2–15.6) |
3 | Long | $200 | 614 | 0.8 (0.3–1.9) | 5.1 (2.1–11.7) |
0 | Long | $200 | 219 | 0.5 (0.1–3.2) | 5.6 (0.8–30.7) |
Total = 2482 |
Cost effectiveness
Sampling protocol | Surveys sent to receive 1 response (n)a | Surveys sent to recruit 1 participant (n)a,d | Costs ($) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Follow-up waves (n) | Survey length | Survey incentive | Initial wave | Follow-up wave 1 | Follow-up wave 2 | Follow-up wave 3 | Total per mailed individual | Per response receiveda | Total to receive 1 responseb | Recruit 1 participantb,d | ||
3 | Short | $2 | 4.61 | 50.7 | 3.01 | 0.70 | 1.01 | 1.01 | 5.74 | 26.44 | 28.89 | 317.51 |
3 | Medium | $2 | 4.88 | 53.6 | 3.09 | 0.70 | 1.09 | 1.09 | 5.96 | 29.09 | 31.84 | 349.88 |
0 | Long | $2 | 12.20 | 134.1 | 3.09 | – | – | – | 3.09 | 37.65 | 39.54 | 434.48 |
3 | Long | $2 | 6.13 | 67.4 | 3.09 | 0.70 | 1.09 | 1.09 | 5.96 | 36.59 | 39.99 | 439.50 |
2 | Long | $2 | 8.33 | 91.5 | 3.09 | 0.70 | 1.09 | – | 4.88 | 40.64 | 44.01 | 483.66 |
0 | Long | Gift card | 32.26 | 354.5 | 1.09 | – | – | – | 1.09 | 40.83c | 46.81c | 503.38 |