In any given season, if you calculate the percentiles for PER (using player minutes played as weights), 9 is usually right around the 5th percentile. I thought that was a reasonable definition of "replacement." Below is a summary of the last 28 years:
Joined: 05 Jan 2005 Posts: 508 Location: Columbus, OH
Posted: Wed Aug 22, 2007 8:31 am Post subject:
basketballvalue wrote:
Justin, this makes sense, but I don't have a feeling for whether 5th percentile is the right place to make the cutoff (as opposed to 10th, say). Could you look at who the actual replacement players were in the last couple of years using the transaction wire archives on NBA.com and find the average of their PER? I'd be interested to see if it's really 5th percentile.
That's a good suggestion, but I don't have time to do such a study at the moment. _________________ Regards,
Justin Kubatko
Basketball Stats!
The replacement level looks like it's inching down. How does one test for statistical significance here?
A couple of quick simple tests both suggest that the result is statistically significant.
A linear regression with year as the explanatory variable is significant at the 1.8% level. (N=28, t-stat=-2.53, adj R2=.166, estimated slope coefficient = -.0189.)
A test that makes fewer assumptions is to simply do a t-test comparing the mean of the earlier years to the mean of the later years; to increase the power of the test it's often useful to exclude the middle one-third of the observations. This test is significant at the 1.6% level (comparing the first 9 observations to the last 9; means = 8.91 and 8.54, variance (pooled) = .0832, t-stat=2.70.)
A 15 PER who played 2500 minutes in the season (or a little over 30 minutes a game, essentially an average performing starter) is conveniently a VAR 1000. There were 82 VAR 1000+ in the league with Al Harrington being at 1000 even.
Kobe Bryant is the the VAR leader at 3.6 times that.
A VAR 500 can be roughly a PER 15 playing 15 minutes a game or a PER 13 playing 25 minutes. That might be a decent point to define "good" / "important" rotation player (at least from a mostly offensive standpoint). There were 173 last season. Among those right near 500 are Balkman, Rondo, J Smith, Najera.
A VAR 250 is still a decent role player in modest minutes. Josh Boone was 251. Robert Horry 221.
VAR near zero but big minutes includes some notable names.
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