Executing the Actual Meta-analysis

Meta-analysts must decide before conducting the analysis whether to employ a fixed-effects or a random-effects analysis model. These dilfer in the degree of influence each individual study s treatment effect is allowed to exert mathematically on the new treatment effect point estimate calcnlated by the meta-analysis this degree of inflnence is operationalized by the weight assigned to each treatment effect. 

Allowing for the existence of differences between studies included in the metaanalysis is an intuitively sensible feature of the random-effects model, since in most circumstances when comparing multiple studies conducted by multiple independent research teams, it would be very surprising if the studies incorporated did not vary from each other. While the precise methods of quantitatively estimating the differences between studies (i.e., the additional component of the determination of the weight assigned to each study s treatment effect point estimate in addition to its precision) need not be discussed here, it is important to be aware of the consequences of employing a fixed-effects model when a random-effects model is the 

6 Meta-analysis, Group Sequential Study Designs, and other topics 

Of note is that both the lower and the upper limits of the confidence interval lie below zero. This result can therefore be interpreted in this manner  

The result from this meta-analysis indicates a statistically significant reduction in all-cause mortality associated with carvedilol in the general population. The result is compatible with a reduction as great as 68% and as small as 6%, and our best estimate is a reduction of 45%. 

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