Thursday, May 12, 2011

Peformance Enhancer Detector: The Baltimore Orioles

The graph below acts as a detector for Performance Enhancing Drug (PED) users.  The subsequent graphs show an obvious user in Rafael Palmiero; somebody who might have been using steroids in Cal Ripken; and a normal career curve for comparison--the great Frank Robinson. We'll start with the chart showing the top 10% and the bottom 10% for adjusted career OPS+ only:

A great way to detect an abnormal career progression; the graph uses OPS+ as a proxy to measure overall batting skill.  Relative OPS+ is measured by comparing 5-year periods of a player's career.  For instance, when 32 is seen on the age axis it represents the player's performance from age 28 through age 32, and age 33 represents ages 29 through 33 and so on.  The "relative" part is introduced when all of the player's other five-year periods are indexed to the player's best five-year period.  The best 5-year period is set to equal 100 and the rest of the 5-year periods are measured accordingly.  The chart above  displays the career progression in which 80% of players fit.  A couple of things to remember when viewing the chart is that the area between the 10% lines is 80% of all players measured. Additionally, the player's performance is compared to himself, so if Player A has an 85 rating at age 32 and Player B has an 89 rating at the same age, that does not necessarily mean that Player  B was a better player; it just means Player B closer to his peak than Player A. Hit the jump to see the individual player charts.

Cal Ripken: Possible User, Fell Below The Lower Limit, Then
Significantly Jumped Above It At Age 38 and 39.

Rafael Palmeiro: Obvious User, Peaked At 37 And Stayed
Above The Norm At 38 Also.

Frank Robinson: Not A User, Peaked Slightly Late But
Never Crossed Upper Threshold.

There's A Stat For That

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