Forest plot

The forest plot shows each study as a square (effect) with a line (95% interval). The larger the square, the greater the weight of the study. The diamond below is the pooled effect, its tips are the interval limits; the thin line below is the prediction interval. The dashed line marks "no effect" (0, for ratios 1).

Example: If the diamond lies clearly on one side of the dashed line, the pooled effect differs from "no effect".

Caution: Check whether a single large study determines the result (large square) and whether the intervals overlap.