Collecting high quality data in surveys of students and low-income populations is critical for many studies in social science.  Research indicates small, monetary pre-incentives are most effective in increasing response rates; less effective are post-incentives and lotteries, which are offered contingent upon completion of the survey.   However, little is known about the effectiveness of large cash post-incentives relative to lotteries for cash or gifts.  Moreover, given growing constraints on research funds, research is needed to determine which types of incentives are most cost-effective.
In this study we consider the effectiveness of various types of post-incentives with a well-educated but low-income population:  college students receiving Pell Grants (a federal means-tested form of financial aid).  In particular, we assess responsiveness to a cash post-incentive relative to lotteries offering monetary or nonmonetary incentives.
A stratified random sample of Pell Grant recipients enrolled in Wisconsin public higher education in 2008 (N=3,000) were mailed a $5 cash pre-incentive and invitation to complete a web survey.  Nonresponders received up to three email reminders and mail SAQ.  Respondents were randomly assigned to the following post-incentive groups:
 Condition 1:  no post-incentive
 Condition 2:  $10 post-incentive
 Condition 3:  inclusion in a lottery for $50 (paid out to 25 winners)
 Condition 4:  inclusion in a lottery for an iPad
The analysis has three parts:
 Effects of the experimental treatments on unit and item nonresponse including:  willingness to participate (proportion accessing initial page of the survey); eagerness to participate (time before completing survey); and willingness to respond (proportion beginning survey). 
 The effects of incentives on survey reports to assess the potential for nonresponse bias, exploring differences among groups in survey responses (i.e. demographics) and differences between responders and nonresponders using administrative data.
 Analysis of cost variation among the treatments.