Tuesday, September 2, 2008

Looking at the outliers

This graph is a little unfamiliar, but it has lots of power to show what's going on behind the data. 71 small community practices are laid out on the horizontal in order of their average LDL-cholesterol. The vertical axis show just what that level was.

The red lines at 100 and 130 mark the guideline-recomended targets. Although most diabetic patients should be below 100 mg/dl, the average patient in most practices is getting there.

Pay extra attention to the right hand end of the line. The last 4 practices have very high levels. In fact, the highest 11 practices seem to have a bit of space between them and the regular run of practices. Perhaps these are the practices that need some extra help in taking care of cholesterol.

We something similar on the left hand side: the lowest ("best") 4 practices seem to be standouts. Maybe we should visit those places and see what they've got going on - so we can bottle it for others to use!

Of course, the graph is just suggestive. There may be other, less interesting, reasons for outliers such as small sample sizes, data errors, miscalibrated lab results, etc. But, the picture does seem to tell us where to look next.

One more example of what you can do from a population view that you can't do one doctor at a time!


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