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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 wavesSurvey lengthField study participation amountSample size (n)Probability of participating in field study (% with 95% CIs)aProbability of participating among survey respondents (% with 95% CIs)b
3Short$1502072.9 (1.3–6.3)13.3 (6.1–26.7)
3Medium$1502102.4 (1.0–5.6)11.6 (4.9–25.1)
3Long$1504272.1 (1.1–4.0)12.5 (6.6–22.3)
2Long$2008051.0 (0.5–2.0)8.2 (4.2–15.6)
3Long$2006140.8 (0.3–1.9)5.1 (2.1–11.7)
0Long$2002190.5 (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)