To be sure, one must be wary of weighted averages or any kind of statistic that by its nature favors inclusion of winners.

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The SPIVA Scorecard provides performance comparisons corrected for survivorship bias, equal- and asset-weighted peer averages and measures of style consistency for actively managed U.S. equity, international equity and fixed income mutual funds.

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Averages weighted by market capitalization. 2.

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The standard deviation in the National League that year was .063, meaning that a "typical" team had a winning percentage between 0.436 and 0.564 (we also weighted the deviation averages by division, since schedules had teams playing more games within their own division than outside of it).

FORBES: Magazine Article