Increasing response rates in a survey of medicaid enrollees: The effect of a prepaid monetary incentive and mixed modes (mail and telephone)

Objectives: We sought to evaluate the effect of pairing a mixed-mode mail and telephone methodology with a prepaid $2.00 cash incentive on response rates in a survey of Medicaid enrollees stratified by race and ethnicity. Research Design: Sampling was conducted in 2 stages. The first stage consisted of a simple random sample (SRS) of Medicaid enrollees. In the second stage. American Indian, African American, Latino, Hmong, and Somali enrollees were randomly sampled. A total of 8412 enrollees were assigned randomly to receive a mail survey with no incentive or a $2.00 bill. Results: The response rate within the SRS after the mail portion was 54% in the incentive group and 45% in the nonincentive group. Response rates increased considerably with telephone follow-ups. The incentive SRS response rate increased to 69%, and the nonincentive response rate increased to 64%. Differences between incentive conditions are more pronounced after the first mailing (P < 0.01); almost all differences remained significant (P < 0.05) after the completion of the mail mode. The inclusion of the $2.00 incentive had similar effects on response rates and cost across the different racial and ethnic strata, except for Latino enrollees. Conclusions: A mixed-mode mail and telephone methodology is effective for increasing response rates in a Medicaid population overall and within different racial and ethnic groupings. The effectiveness of this strategy can be enhanced, in terms of response rate and cost, by including a $2.00 prepaid incentive.