Table 4 

Summary Outcome Measures for Emergency Room Visits. 

Measure 
Effect Size 
Confidence Interval 
Effect Size Pvalue 
Homogeneity Test Pvalue 


SMD^{a} 

Fixedeffects 
0.21 
0.33, 0.09 
<0.001 
0.05 
Randomeffects 
0.27 
0.45, 0.09 
0.003 
0.05 
IRD^{b} 

Fixedeffects MH 
0.04 
0.05, 0.03 
<0.001 
<0.001 
Randomeffects 
0.05 
0.08, 0.03 
<0.001 
<0.001 
IRR^{c} 

Fixedeffects MH 
0.66 
0.59, 0.74 
<0.001 
<0.001 
PR + study indicators 
0.66 
0.54, 0.81 
<0.001 
<0.001 
PR – study indicators 
0.77 
0.59, 0.99 
0.039 
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 MantelHaenszel procedure to estimate a fixedeffects model and an inversevariance method to estimate a randomeffects model. ^{c }IRR refers to the incidence rate ratio and was obtained using MantelHaenszel procedure to estimate a fixed effects model and Poisson regression models with HuberWhite sandwich estimators with and without study indicators which is equivalent to a randomeffects model. 

Guevara et al. BMC Medical Research Methodology 2004 4:17 doi:10.1186/14712288417 