Performance Perspectives Blog

Why it is good to look at outliers

by | Jul 31, 2012

In the past two weeks I’ve conducted two software certifications for TSG clients, and in both cases they had controls to test portfolio returns against specified benchmark tolerances. And, as you might expect, the fact that a portfolio blows past a tolerance level doesn’t mean it’s wrong; merely that it’s worthy of review. After all, we expect to see outliers appear.

The London Olympic games already have a case of someone going past a benchmark, but really not a benchmark we’d typically expect to see. The London Mail had an article about 16-year old Chinese female swimmer Ye Shiwen’s performance that not only beat the female record, but also surpassed American swimmer Ryan Lochte’s time in the last 50 meters. “Ye Shiwen posted such a good time that her final 50m was in fact faster than Lochte’s performance in the men’s event, at just 28.93 seconds…Her achievement was so unprecedented that it even led some broadcasters to question whether Ye had benefited from underhand practices.”

Perhaps Ye did not benefit from any banned substance. But such an extraordinary performance is worthy of review, and this is what will occur. Controls such as this in performance measurement should almost be routine, as a way to catch errors.

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