. 2018 Jun 20;18:59. doi: 10.1186/s12874-018-0524-8

Table 2.

Comparison of response rates by invitation mode and survey type

	Total		Email invitation		Postal invitation		p-value
	Number sent	Response rate^a	Number sent	Response rate^a	Number sent	Response rate^a	Email vs postal
Overall	1328	30.2	649	34.8	679	25.8	< 0.001
Length & type
Short, closed	316	27.9	154	28.6	162	27.2	0.78
Short, open	330	31.2	162	36.4	168	26.2	0.05
Long, closed	334	31.4	154	35.1	180	28.3	0.19
Long, open	348	30.2	179	38.6	169	21.3	< 0.001

^aAAPOR response rate2 (number completed + number partial completes/sample size)