Table 2.

Response rates for incentive groups in study 1 and study 2

Incentive Group		Total Randomized	Number of Responses	Response Rate	Difference	95% Confidence Interval
Study 1
	Incentives (collectively)	615	175	29%	2%	–3% to 7%
	No incentive	611	162	27%
	£5 Amazon voucher	206	66	32%
	£5 charity donation	204	55	27%
	£250 prize draw	205	54	26%
Study 2
	£10 Amazon voucher	1296	476	37%	9%	5% to 12%
	No incentive	1295	364	28%