Tuesday, August 31, 2010
Derek Jeter’s 2010 Actual vs. Projected Through August 30
Since Mel Hall mentioned this in an earlier thread and it was something I was planning to look at anyway, here’s how Derek Jeter’s 2010 year to date performance compares to his average projection heading into the season, pro-rated to his actual YTD playing time.
| Projection | PA | AB | H | 1B | 2B | 3B | HR | BB | HBP | SO | SB | CS | DP | AVG | OBP | SLG |
| average | 602 | 539 | 164 | 124 | 26 | 2 | 12 | 53 | 7 | 84 | 15 | 4 | 18 | .304 | .372 | .426 |
| ytd | 602 | 545 | 146 | 109 | 24 | 3 | 10 | 48 | 6 | 84 | 14 | 4 | 19 | .268 | .332 | .378 |
| difference | -6 | 18 | 15 | 2 | -1 | 2 | 5 | 1 | 0 | 1 | 0 | -1 |
Difference is just the projected stat minus the actual stat. So if you look at the hits column, Jeter has had 18 fewer hits than projected, 15 of them singles. He’s also hit two fewer HRs and doubles than projected, and walked five fewer times. K rate is spot on and SB/CS is right there. He’s hit into one more DP than projected.
If we think of Jeter’s average projection as a baseline, we can look at his projection in terms of a binomial distribution of each component stat.
| StDev | PA | AB | H | 1B | 2B | 3B | HR | BB | HBP | SO | SB | CS | DP | AVG | OBP | SLG |
| +2 Std | 602 | 539 | 189 | 129 | 36 | 5 | 19 | 68 | 12 | 66 | 22 | 0 | 10 | .351 | .447 | .541 |
| +1 Std | 602 | 539 | 176 | 126 | 31 | 3 | 15 | 61 | 10 | 75 | 18 | 2 | 14 | .327 | .410 | .483 |
| Baseline | 602 | 539 | 164 | 124 | 26 | 2 | 12 | 53 | 7 | 84 | 15 | 4 | 18 | .304 | .372 | .426 |
| -1 Std | 602 | 539 | 151 | 121 | 21 | 1 | 8 | 46 | 4 | 93 | 11 | 7 | 22 | .280 | .334 | .368 |
| -2 Std | 602 | 539 | 138 | 117 | 16 | 0 | 5 | 39 | 2 | 103 | 7 | 9 | 27 | .256 | .296 | .314 |
This is how I figure out my CAIRO percentile projections, although I also include a function to allocate playing time based on how a player’s projection looks (ie, a player who’s exceeding his projection will probably play more, a player who’s underperforming will play less). In this case since we’re looking at Jeter’s YTD performance, I’m holding the playing time constant.
As you can see, Jeter’s performance is within one standard deviation of his projection, albeit on the negative side.
So the question is probably whether or not those 18 missing hits and three missing extra base hits are the product of a decline in bat speed or just a representation of the fluctuation that can happen in a baseball season. Probably a bit of both, although perhaps the decline in bat speed is overstated somewhat by his actual results so far.
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