When Things Are Not as They Appear: Assessing the Adequacy of Cluster Randomization When Outcome Events Are Rare at Baseline

Table 1

Age (SD) and gender distribution (%) at baseline and across intervention conditions among 933 youth participating in the FOYC+CImPACT versus WW+GFI trial (control).

		Total		Boys		Girls
	Total	WW	FOYC	WW	FOYC	WW	FOYC
Sample
Baseline	933(100.0)	497(100.0)	436(100.0)	228(45.9)	231(53.0)*	269(54.1)	205(47.0)*
6 months	884(94.7)	464(93.4)	420(96.3)	215(46.3)	221(52.6)	249(53.7)	199(47.4)
12 months	831(89.1)	432(86.9)	399(91.5)	202(46.8)	216(54.1)*	230(53.2)	183(45.7)*
18 months	785(84.1)	416(83.7)	369(84.6)	193(46.4)	202(54.7)*	223(53.6)	167(45.3)*
24 months	806(86.4)	417(83.9)	389(89.2)	190(45.6)	206(53.0)*	227(54.4)	183(47.0)*
36 months	752(80.6)	402(80.9)	350(80.3)	176(43.8)	182(52.0)*	226(56.2)	168(48.0)*
Age
Baseline	10.5(0.7)	10.4(0.6)	10.5(0.8)*	10.4(0.7)	10.6(0.8)*	10.4(0.6)	10.43(0.8)
6 months	11.1(0.7)	11.0(0.7)	11.2(0.7)*	11.1(0.7)	11.2(0.7)*	11.0(0.7)	11.07(0.7)
12 months	11.6(0.7)	11.6(0.7)	11.7(0.8)*	11.6(0.7)	11.7(0.8)*	11.6(0.7)	11.62(0.8)
18 months	12.1(0.7)	12.1(0.7)	12.2(0.8)*	12.0(0.7)	12.3(0.8)**	12.1(0.6)	12.10(0.8)
24 months	12.6(0.7)	12.6(0.7)	12.7(0.8)*	12.7(0.7)	12.75(0.8)	12.5(0.6)	12.64(0.8)
36 months	13.6(0.7)	13.5(0.6)	13.7(0.8)*	13.6(0.7)	13.7(0.8)	13.5(0.6)	13.65(0.8)

* 𝑃<0.05, **𝑃<0.01