Meta-analytic methods for pooling rates when follow-up duration varies: a case study

Table 3 Summary Outcome Measures for Days of School Absence.

Measure	Effect Size	Confidence Interval	Effect Size P-value	Homogeneity Test P-value
SMD^a
Fixed-effects	-0.14	-0.23, -0.04	0.006	0.61
Random-effects	-0.14	-0.23, -0.04	0.006	0.61
IRD^b
Fixed-effects M-H	-0.15	-0.19, -0.11	<0.001	<0.001
Random-effects	-0.17	-0.25, -0.08	<0.001	<0.001
IRR^c
Fixed-effects M-H	0.86	0.83, 0.90	<0.001	<0.001
PR + study indicators	0.86	0.77, 0.97	0.011	<0.001
PR - study indicators	0.86	0.75, 0.99	0.044	N/A

^a SMD refers to standardized mean difference and was obtained using both fixed effects and random effects models. ^b IRD refers to the incidence rate difference, and was obtained using a Mantel-Haenszel procedure to estimate a fixed-effects model and an inverse-variance method to estimate a random-effects model. ^c IRR refers to the incidence rate ratio and was obtained using Mantel-Haenszel procedure to estimate a fixed effects model and Poisson regression models with Huber-White sandwich estimators with and without study indicators which is equivalent to a random-effects model.

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