Conversion to a common metric in meta-analysis is the process whereby researchers aggregate certain statistics of many separate research findings and translate them into the same metric so treatment effects can be estimated. Meta-analysis is a type of study whereby research studies are used as data points instead of individuals. Meta-analysis statistically synthesizes the results from an accumulation of research reports. This is fundamentally different from narrative reviews of research literatures, which although quite useful for describing many details about a body of literature, are unable to apply statistics to evaluate a series of studies. Quantitative research synthesis like meta-analysis is important because not all research studies agree, and the conclusions of narrative reviews may reflect hopeful myths instead of empirically accurate realities ...