Table 2 Results of Polyp Prevention Trial
From: A simple method for analyzing data from a randomized trial with a missing binary outcome
stratum s | adenoma | difference in observed | weight | bias factor ε(max)s | ||||
|---|---|---|---|---|---|---|---|---|
stratum s | recurrence | rates of recurrence d s | w s | |||||
sex | age | group | no | yes | missing | |||
control | 573 | 374 | 94 (9%) | |||||
study | 578 | 380 | 76 (7%) | |||||
men | 30–49 | control | 33 | 22 | 5 (8%) | -.23 | .07 | .09 |
study | 58 | 12 | 3 (4%) | |||||
40–59 | control | 99 | 76 | 7 (4%) | .01 | .17 | .05 | |
study | 94 | 76 | 9 (5%) | |||||
60–69 | control | 122 | 105 | 25 (10%) | -.04 | .23 | .11 | |
study | 144 | 105 | 18 (7%) | |||||
70–79 | control | 65 | 76 | 26 (16%) | -.04 | .13 | .20 | |
study | 70 | 71 | 29 (17%) | |||||
women | 30–49 | control | 54 | 11 | 3 (4%) | .03 | .10 | .07 |
study | 47 | 12 | 4 (6%) | |||||
40–59 | control | 69 | 24 | 4 (4%) | .02 | .11 | .04 | |
study | 69 | 27 | 4 (4%) | |||||
60–69 | control | 77 | 31 | 13(11%) | .08 | .12 | .11 | |
study | 68 | 40 | 5 (4%) | |||||
70–79 | control | 54 | 29 | 11(12%) | .22 | .07 | .12 | |
study | 28 | 37 | 4 (6%) | |||||
- The overall estimate of the difference in probabilities of recurrence between study and control groups is
= Σ
s
d
s
w
s
= -.003 with a standard error .022. We define ε(max)s
= max((1 - π0s
)/π1s
, (1 - π1s
)/π0s
), where π
zs
equals one minus the fraction missing in group z and stratum s. The anticipated maximum bias is ψ
max
Σ
s
ε(max)s
w
s
= ± .10 ψ
max
, where ψ
max
is the anticipated bias if there were complete confounding of the unobserved covariate and treatment.
= Σ
s
d
s
w
s
= -.003 with a standard error .022. We define ε(max)s
= max((1 - π0s
)/π1s
, (1 - π1s
)/π0s
), where π
zs
equals one minus the fraction missing in group z and stratum s. The anticipated maximum bias is ψ
max
Σ
s
ε(max)s
w
s
= ± .10 ψ
max
, where ψ
max
is the anticipated bias if there were complete confounding of the unobserved covariate and treatment.