Table 1

Baseline demographics and response rates
Whole sample (n=1246) Survey responders (n=416) Survey non-responders (n=830) Comparison between responders and non-responders
Age
mean (SD) 42.9 (13.1) 46.3 (13.1) 41.2 (12.8) t1244=−6.59, p<0.0001
range 21-88 23-78 21-88
median 42 45.5 39
Gender
male n (%)* 514 (41.3) 166 (39.9) 348 (41.9) X12 =0.468, p=0.49

*Percentages are percentage of group (column) totals.

Mathieu et al.

Mathieu et al. BMC Medical Research Methodology 2012 12:162   doi:10.1186/1471-2288-12-162

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