Deposit? Yes, please! The effect of different modes of assigning reward-and deposit-based financial incentives on effort 291 9 Data analysis Descriptive statistics are provided for the sample of respondents at each time point and chi-squared tests are used to assess differences between these samples. The main outcome measures are: 1) effort, and 2) earnings. Effort is operationalised as persistence (we will use these terms interchangeably), is operationalised as the number of sliders a respondent completed at T1. We also report the number of pages (rather than the number of sliders), because the experiment was set-up such that after each page respondents were asked if they wanted to complete another page of sliders, and respondents would generally finish the whole page or quit the experiment. Earning reflects the total monetary reward earned. Following the study design, we first contrast the random and nudged assignment arm, followed by contrasting the reward- and deposit-based incentives within the random arm, and finally contrast the reward- and deposit-based incentive schemes within the nudged arm. Each contrast is explored descriptively, followed by regression models explaining effort or earnings based on each contrast. Finally, we performed linear regression models investigating the impact of each contrast on persistence and earnings corrected for payment condition. Appendix B (Online Supplements) also contains a set of additional results, e.g., Kaplan-Meier survival curves for ‘survival’ in the experiment (i.e., continuing the slider tasks) and a set of regression analyses where persistence and earnings are modelled whilst controlling for demographics. Results Demographics A total of 228 students participated in the first session, of whom the majority were master students with an income below €15,000 annually and were aged 18 to 24. Gender was roughly equally distributed with a slight majority of females. Of these respondents, 171 returned for the second session one week later (drop-out rate 25%). No evidence was found for selective drop-out according to the characteristics listed in Table 2, except by education (p = .031). First year students had a higher tendency to drop out. Although more respondents dropped out in the nudged assignment (see Table 2), this difference was not significant. The propensity to drop out was also not associated with assignment arm or payment condition.2 2 Figure 1 shows that drop-out appears to be considerably higher among respondents in low payment conditions that were either randomized to or chose deposit-based incentives. In Appendix C (Online Supplements), we explored the degree to which this selective drop-out affects our findings. Although we find some evidence of selection effects, we find no evidence of bias in our results.
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