GraphPad Prism 8 User Guide

Forest plots

Forest plots

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Forest plots

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This graph below is a Forest plot, also known as an odds ratio plot or a meta-analysis plot. It graphs odds ratios (with 95% confidence intervals) from several studies.

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There are a few tricks to making this graph:

1.Enter the data into a Column table. Keep the default choice to enter the "replicates" into columns. (In this case, they are not replicates, but Prism thinks they are).

2. Enter the results for each study into a separate data set column. Enter in each column the Odds ratio itself, as well as the high and low confidence limits (computed elsewhere).  The order of those three values doesn't matter. Label the studies by entering column titles. You may use Greek symbols, super and subscript, etc.

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2.Go to the graph.

3.When you first go to look at the graph, Prism will prompt for the kind of graph you want. Choose "Column Mean with error bars".

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4.Note that Prism's doesn't (can't) know that each column contains a computed odds ratio along with the low and high confidence limits. It just sees three values. So choose to plot the median and range. The median and range of the three values you entered are the odds ratio and its confidence limits computed elsewhere. If you choose to plot a confidence interval instead, Prism will compute a confidence interval from the three values you enter and the results will be nonsense.

5.The default graph is vertical. To make the graph horizontal (as below), double click on the graph to bring up Format Graph, and go to the third tab.
 
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6.Double-click on the X axis to bring up Format Axis. Choose to make the axis scale logarithmic with log spaced minor ticks, and to create a grid line at X=1.0.

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