In a forest plot, the results of component studies are shown as squares centred
on the point estimate of the result of each study  a horizontal line
runs through the square to show its confidence interval  the confidence interval
represented is generally, but not always, a 95% confidence interval
 shows
the estimated effect of interest for each of the separate studies in the metaanalysis
 in the centre of the confidence interval for each study is
a square
 size of the square corresponds to the size of the study
and therefore the precision of the estimate
 the diamond symbol
is used to represent the overall estimate from the metaanalysis and its confidence
interval
 centre of the diamond represents the pooled point estimate,
and its horizontal tips represent the confidence interval
 significance
is achieved at the set level if the diamond is clear of the 'line of no effect'

a vertical line, known as the 'line of no effect'  represents equal effectiveness
of the treatments (for example, it would correspond to a value of zero for a difference
in means, or unity if the effect of interest were the odds ratio)
 if an
individual study has a confidence interval that crosses the 'line of no effect'
then the results of that particular study were not statistically significant (at
the chosen confidence interval)
 plot allows readers to see
the information from the individual studies that went into the metaanalysis at
a glance
 provides a simple visual representation of the amount of variation
between the results of the studies, as well as an estimate of the overall result
of all the studies together
 more
information about the Forest plot click here
