- This is a convenient visual scatter diagram used in meta-analysis that compares the risks observed in the experimental and control arms of clinical trials. Each trial is located in the space of a diagram as shown here where the sizes of the circles (three in this case) indicate the sizes of the trials. Trials in which the experimental treatment had a higher risk than the control will be in the upper left of the plot. If risk in the both groups is the same the circle will fall on the line of equality. If the control treatment has a higher risk than the experimental treatment then the point will be in the lower right of the plot. It is often used as an indicator of heterogeneity and hence as an indicator of the likelihood that results from different trials can be validly combined. Named after Kristin L'Abbé.