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Table 1 Representativeness of participant sample (Access 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 3461 585 557 72    
   Mean (SD) Mean (SD) Mean (SD) Mean (SD) p p p
Age (Years) 52.6 (13.4) 48.0 (15.0) 48.2 (15.1) 44.7 (14.0) <.0001 .07 .06
   N (%) N (%) N (%) N (%) p p p
Gender Male 3258 (94.1) 483 (82.6) 465 (83.5) 55 (76.4) <.0001 .20 .14
Female 203 (5.9) 102 (17.4) 92 (16.5) 17 (23.6)    
Race Native American 26 (0.8) 26 (4.4) 23 (4.1) 2 (2.8) <.0001 .75 .76
Asian/Pacific Islander 61 (1.8) 61 (10.4) 61 (11.0) 7 (9.7)    
Black 850 (24.6) 101 (17.3) 91 (16.3) 13 (18.1)    
White 2161 (62.4) 369 (63.1) 356 (63.9) 45 (62.5)    
Unknown 412 (11.9) 66 (11.3) 64 (11.5) 12 (16.7)    
Ethnicity Hispanic 55 (1.6) 55 (9.4) 51 (9.2) 9 (12.5) <.0001 .40 .37
Not Hispanic 3117 (90.1) 481 (82.2) 458 (82.2) 57 (79.2)    
Unknown 289 (8.4) 49 (8.4) 48 (8.6) 6 (8.3)    
MH Use MH Use 1671 (48.3) 277 (47.4) 262 (47.0) 46 (63.9) .01 .01 .01
No MH Use 1790 (51.7) 308 (52.7) 295 (53.0) 26 (36.1)    
Rural/Urban Rural 1191 (34.4) 236 (40.3) 229 (41.1) 32 (44.4) .09 .45 .59
Urban 2239 (64.7) 349 (59.7) 328 (58.9) 40 (55.6)    
Missing 31 (0.9) 0 0 0    
  1. *Note that p-values are calculated from independent samples t-tests for continuous variables and chi squared tests for categorical variables