In the early days of meta-analysis (at least in its current incarnation) Robert Rosenthal was asked if it makes sense to perform a meta-analysis, given that the studies differ in various ways, and the analysis amounts to combining apples and oranges. When does it make sense to perform a meta-analysis We start with an example to show how meta-analysis and narrative review would approach the same question, and then use this example to highlight the key differences between the two. Meta-analysis is able to address these issues whereas the narrative review is not. On the other hand, if it varies substantially from study to study, we want to quantify the extent of the variance and consider the implications.
If it is consistent, then we want to estimate the effect size as accurately as possible and to report that it is robust across the kinds of First, we need to know whether or not the effect size is consistent across the body of data. The goal of a synthesis is to understand the results of any study in the context of all the other studies. Why perform a meta-analysis? What are the advantages of using statistical methods to synthesize data rather than taking the results that had been reported for each study and then having these collated and synthesized by an expert? While the loss of more than 100,000 children would be unspeakably sad in any event, the real tragedy lies in the fact that many of these deaths could have been prevented. Governments in various countries launched educational initiatives such as the Back to sleep campaigns in the UK and the US, which led to an immediate and dramatic drop in the number of SIDS deaths. In the early 1990s, researchers became aware that the risk of SIDS decreased by at least 50% when babies were put to sleep on their backs rather than face down.
The advice was not unusual, in that many pediatricians made similar recommendations at the time.ĭuring this same period, from the 1950s into the 1990s, more than 100,000 babies died of sudden infant death syndrome (SIDS), also called crib death in the United States and cot death in the United Kingdom, where a seemingly healthy baby goes to sleep and never wakes up. This statement was included in most editions of the book, and in most of the 50 million copies sold from the 1950s into the 1990s. Benjamin Spock wrote ‘I think it is preferable to accustom a baby to sleeping on his stomach from the beginning if he is willing’. In his best selling book Baby and Child Care, Dr. Papers on meta-analysis What is meta-analysis
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