Regression Towards The Mean

I spent a lot of time this afternoon comparing the rates at which different physicians have been discharging inpatients directly home from the Acute Medical Unit this year. Discharging them home as opposed to transferring them onwards to an inpatient ward, that is. And there was quite a lot of variation between the different consultants' rates. From about 35% to about 50%. But what was interesting was that there was more variation between their rates when I looked at last year's figures - from about 25% to 50%. A lot of physicians who'd had extreme values last year showed middling values this year.

This phenomenon is called "regression towards the mean" and it was discovered by the Victorian polymath Sir Francis Galton, whose picture you see here. Francis Galton died in January 1911 so you can think of this as a sort of centenary homage blip.