Incentives in Web Studies: Methodological Issues and a Review

Two meta-analyses review the effectiveness of incentives in Web studies. The first analysis summarizes 32 experiments on the impact of material incentives on response. It is based on a sample of 212,810 people. A significant effect (odds ratio = 1.19; 95% confidence interval: 1.13—1.25) is revealed, indicating that incentives motivate people to start a Web survey. The second analysis comprises 26 experiments on the impact of incentives on retention and is based on a sample of 7,073 people. It yields a significant effect (odds ratio = 1.27; 95% confidence interval: 1.12—1.44), indicating that once people have accessed a survey for whatever reasons, they are more likely to finish if an incentive is offered. The established incentive effects are stable across various study characteristics. Conclusions did not appear to be due to publication bias.