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Table 2 Representativeness of participant sample (Tailoring study)

From: Practical application of opt-out recruitment methods in two health services research studies

  Veterans eligible to receive opt-out letter Veterans mailed opt-out letter Veterans who received opt-out letter Veterans who participated p-value (eligible vs. participated)* p-value (mailed opt-out vs. participated) p-value (received opt-out vs. participated)
N 70119 3703 3533 762    
   Mean (SD) Mean (SD) Mean (SD) Mean (SD) p p p
Age (Years) 51.6 (13.8) 50.8 (13.8) 51.0 (13.8) 51.6 (12.5) .35 .48 .70
   N (%) N (%) N (%) N (%) p p p
Gender Male 62280 (88.8) 2947 (79.6) 2806 (79.4) 574 (75.3) <.0001 <.01 .01
Female 7839 (11.2) 756 (20.4) 727 (20.6) 188 (24.7)    
Race Native American 1488 (2.1) 66 (1.8) 64 (1.8) 13 (1.7) .08 .82 .86
Asian/Pacific Islander 833 (1.2) 42 (1.1) 40 (1.1) 8 (1.1)    
Black 12170 (17.4) 474 (12.8) 451 (12.8) 105 (13.8)    
White 50271 (71.7) 2811 (75.9) 2688 (76.1) 582 (76.4)    
Unknown 5357 (7.6) 310 (8.4) 290 (8.2) 54 (7.1)    
Ethnicity Hispanic n/a n/a n/a 46 (6.0) n/a n/a n/a
Not Hispanic n/a n/a n/a 712 (93.4)    
Unknown n/a n/a n/a 4 (0.5)    
MH Use MH Use 46672 (66.6) 2498 (67.5) 2375 (67.2) 532 (69.8) .06 .20 .17
No MH Use 23447 (33.4) 1205 (32.5) 1158 (32.8) 230 (30.2)    
Rural/Urban Rural 20426 (29.1) 1070 (28.9) 1023 (29.0) 230 (30.2) .39 .45 .46
Urban 49279 (70.3) 2611 (70.5) 2489 (70.5) 525 (68.9)    
Missing 414 (0.6) 22 (0.6) 21 (0.6) 7 (0.9)    
  1. *Note that p-values are calculated from independent samples t-tests for continuous variables and chi squared tests for categorical variables