A forest plot is a graphic representation of data from a meta-analysis in which the researchers need to show the results of multiple different studies in a way that allows comparison of each individual study to the others. Hence it allows you to see “the forest” as well as each tree.
Deeper dive
In a forest plot, each line is one study (usually with the authors and date included) from the meta-analysis that also includes basic information about the study, such as the population size, the hazard ratio or odds ratio, a mean (average) and/or standard deviation related to the results, etc. What’s included depends on what the authors are focused on or what they’re comparing. Sometimes a forest plot includes a column indicating the percentage weight it contributed to the overall findings of the meta-analysis, perhaps based on number of participants or some other characteristic. Then further to the right, each study is compared based on the common outcome measure used for the results (odds ratio, standard deviation, etc.). Squares indicate the result from each study with lines extending in either direction that represent the confidence interval or range of the results. A diamond is used on the forest plot to indicate where the overall findings of the meta-analysis fall (combining all of them).