Short report: encouraging GPs to complete postal questionnaires--one big prize or many small prizes? A randomized...

Low response rates to surveys are a problem in general practice. There is evidence that offering GPs incentives improves response rates to postal questionnaires. However, there is less evidence about the most effective form of incentive.

Our trial aimed to maximize response to a postal questionnaire and to test the most effective form of incentive.

The study involved a randomized controlled trial of a postal survey

The incentive of a lottery for six bottles of champagne generated a response rate of 79%. Furthermore, one chance of six bottles generated 9% more responses than six chances of one bottle.

This study has established that, among incentives for postal questionnaires, one big prize improves the yield more than many small prizes despite the lower odds of winning. It has also confirmed that offering a modest incentive to GPs generates good response rates for postal questionnaires.