Funnel plots for comparing institutional performance.
'Funnel plots' are recommended as a graphical aid for institutional comparisons, in which an estimate of an underlying quantity is plotted against an interpretable measure of its precision. 'Control limits' form a funnel around the target outcome, in a close analogy to standard Shewhart control charts. Examples are given for comparing proportions and changes in rates, assessing association between outcome and volume of cases, and dealing with over-dispersion due to unmeasured risk factors. We conclude that funnel plots are flexible, attractively simple, and avoid spurious ranking of institutions into 'league tables'.
Spiegelhalter
David J
DJ
MRC Biostatistics Unit, Institute of Public Health, Cambridge CB2 2SR, UK. david.spiegelhalter@mrc-bsu.cam.ac.uk
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