Table 1

Age, gender, and race distribution of sample population

2 × 2 Factorial Design


Overall

2 page/Letter

2 page/Postcard

4 page/Letter

4 page/Postcard


Overall (N)

780

188

191

199

202



Gender


Female

392 (50.3)

96 (51.1)

97 (50.8)

101 (50.8)

98 (48.5)


Male

388 (49.7)

92 (48.9)

94 (49.2)

98 (49.2)

104 (51.5)



Age


25 - 29

114 (14.6)

24 (12.8)

31 (16.2)

24 (12.1)

35 (17.3)


30 - 39

199 (25.5)

50 (26.6)

49 (25.6)

52 (26.1)

48 (23.8)


40 - 49

211 (27.1)

49 (26.1)

49 (25.6)

61 (30.6)

52 (25.7)


50 - 59

187 (24.0)

47 (25.0)

48 (25.1)

45 (22.6)

47 (23.3)


60 - 65

69 (8.8)

18 (9.6)

14 (7.3)

17 (8.5)

20 (9.9)


Mean (SD)

43.8 (11.2)

44.3 (11.3)

43.3 (11.1)

43.9 (10.9)

43.8 (11.6)



Race


White

582 (74.6)

140 (74.5)

151 (79.1)

147 (73.9)

144 (71.3)


Non-white *

58 (7.4)

17 (9.0)

10 (5.2)

15 (7.5)

16 (7.9)


Unknown/Other

140 (18.0)

31 (16.5)

30 (15.7)

37 (18.6)

42 (20.8)


Note: In the factorial design, the distributions of gender, age, and race were not statistically significantly different between survey lengths or notification types.

* "Non-white" includes: American Indian/Alaskan Native, Black or African American, Native Hawaiian/Pacific Islander, and Asian.

Beebe et al. BMC Medical Research Methodology 2010 10:50   doi:10.1186/1471-2288-10-50

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