Table 2.

Effect of questionnaire length on response rates to the follow-up postal questionnaire, Navajo EARTH Study, 2005–2006.

	Long		Short		pa
	Total (N = 794)		Total (N = 792)
	No.	%	No.	%
Final response status
Questionnaire received
After mailing 1b	189	23.4	240	30.3	<0.01
After reminder postcardc	92	11.6	93	11.7	0.38
After mailing 2d	101	13.1	112	14.1	0.20
Final disposition
Nonresponders
Bad addresse	35	5.2	41	6.1
Deceased	0	0	1	0.1
Returned refused	5	0.6	0	0
Not returned	372	46.1	305	37.6
Total not complete	412		347
Responders
Total completed	382	48.1	445	56.2	<0.01
Response rate		48.1		56.2

^aTwo-sided p-value from two-sample test of proportions comparing long to short.

^b776 long and 767 short questionnaires mailed with incentive.

^cReminder postcards mailed to 577 long and 513 short group nonresponders with good addresses.

^d485 long and 420 short questionnaires mailed to those with good addresses.

^eIncludes 18 long and 25 short questionnaires never mailed due to bad address and those returned without updated follow-up address.