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Table 5 Predicted probability and 95% confidence intervals (CI) of a recipient participating in the field study

From: Effectiveness of incentives and follow-up on increasing survey response rates and participation in field studies

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   
  1. Data stratified by number of follow-up waves, survey length, and field study participation amount. Data calculated excluding non-deliverable surveys and gift card incentive rounds. Data ordered from highest to lowest probability of participating in field study
  2. aBased on total number of surveys mailed (n = 2482)
  3. bBased only on completed surveys (n = 407)