>(My general editorial comment that there is no real way to fix Tendex

a general comment on the Tendex rating:

>because no one knows what it is supposed to measure.)

i happen to like the Tendex rating, or - as it has also been called - a performance rating or production rating - for exactly what it measures, production. many people have tried to come up with a single number that measures overall player ability, and i feel this rating is the closest to doing just that - while also still being simple enough to calculate (so any fan can do it) and by using all of the stats that are readily available to fans. linear weights can be used to fine tune the formula, but it would need to be adjusted every year and would lok like mumbo-jumbo to most fans - keeping it simple makes it available to everyone while i believe not skimping on accuracy...

first off - what it is not. tendex (pts + reb+ ast + st + bs- to - pf - missedFT - missedFG) is obviously not an overall rating of player ability, for the simply reason that it does not measure a player's defensive ability other than ST and BS, and that is certainly a major part of the game that the formula is missing....

BS and ST are the only statistical parameters of "defense" widely available today for individual players, and everyone knows that they do not necessarily measure overall player defense, i.e. a number of players who get alot of steals are known not to be good overall defensive players, and some shot blockers are not good straight up defenders. but the bottom line is that a ST results in a change of ball possession and that is worth approximately one point on average to a team as each team possession is worth on average approximately one point (this arguement is predicated on that premise). a BS prevents a basket from being scored, and although an offensive rebound can follow a BS thus "negating" the effect of the BS, a number of shots are altered by defenders going for a block such that the effect is the same - preventing a basket from being scored. thus i believe a BS is also worth approximately one point...

since 1977-78 (when TOs were first kept as a stat by the NBA) there have been 1096316 fouls called and 985368 FTM. since FTM only result from a foul being called, each foul leads to approximately 9/10 of a point being scored by the opposition. its actually a little more because some of those one million plus fouls called were offensive fouls, so a good approximation is that a PF called is worth approximately one point to the opposition. often there are times when it is good to foul, but overall this scenario holds water. and since a TO is a loss of team possession, and a team possession is worth approximately one point, a TO is worth a loss of one point...

obviously a missed FT is a missed opportunity for one point, and a missed FG is a loss of ball possession (getting an OFF REB after a missed FG simply starts this cycle again). thus PF and TO and missed FT and missed FG can each be shown to be approximated as a loss of a single point...

OFF REBs regain a possession, and a DEF REB is a gain of ball possession. since a player cannot get an AST and a FGM at the same time, and an AST leads to a score, it can be shown to be worth approximately one point....

consequently Tendex is a rating of production and not overall player ability, i.e. what a player produces statistically (for those parameters measured) for his team. each stat has been shown to have a value close to one point...

if you look at the Tendex per minute ratings of players since the 77-78 season, i doubt anyone can argue that those players with the highest ratings are indeed true superstars. only very rarely has a player gotten a very high rating with doubt cast on his value to his team - aka "no D" kiki vandeweghe on the 83-84 nuggets had a 0.685 Tendex/min rating on a team that scored 124 pts/game while giving up 125. but he did score over 29 pts/g and shoot close to 56% and play full time and thus his production was quite high...

Tendex leaves alot to be desired if you're looking for a single number to rate overall player ability, but as a measure of player production, it is probably the perfect parameter to use since it incorporates all available stats. last year teammates kobe bryant and shaquille o'neal scored 28-29 pts/g each, but o'neal's tendex/min rating was a whopping 30% greater (.697 to .539) showing his true production to the team compared to bryant. if bryant was a significantly better defender than o'neal that could offset this huge difference, but in fact both are excellent defenders...

allen iverson (.481 tendex/min) may have led the league in scoring last season, but his overall production was only similar to players such as paul pierce, glenn robinson, stephon marbury, and (surprise) andre miller - his high scoring being "negated" by his poor shooting (same with jerry stackhouse - .458). for those thinking david robinson is over the hill, the spurs led the league in wins last year not just because of duncan (.592 tendex/min - 5th best in the league) but also because of the admiral (.573 - 8th best in the league despite scoring just 14 pts/g) - two players in the same starting lineup with 2 of the top 8 tendex/min ratings in the league...

bob chaikin

bchaikin@...

- --- In APBR_analysis@y..., "Michael K. Tamada" <tamada@o...> wrote:
>

stuff? ;) But

> Hey didn't you go to Caltech and shouldn't you know this

> you did nail the correct answer to the ellipse modeller: Kepler.

Hey, going to Caltech means I know the formulas, how to derive them

>

from first principles, what all the little math symbols mean, and how

to go 40 hours without sleeping. It doesn't mean I know the names of

the famous dead guys. Heck, by going to Caltech, I have a right to

forget names.

>

of

> I'm not sure about this one. Because an overly "conservative" list

> good defensive players will STILL get arguments -- from people who

minimize the

> complain that the list left out players X, Y, and Z, who are great

> defenders.

>

> It's analogous to statistics: you can be "conservative" and

> probability of a Type I error by choosing a small significance

level. But

> in doing so, you are automatically raising the probability of a

Type II

> error.

This is pretty much my point. In policy making, a policy maker

>

really wants to reduce one of those types of errors. Usually the

policy makers don't care about the cost-benefit of Type I vs. Type II

errors. Their job is minimize one type and fight with everyone else

who wants to minimize the other type.

Not sure how that relates to any hoops stuff we're doing right now,

but it might in the future, when we start using all those funky math

symbols.

> Well there's another kind of consistency, one which is a good thing

to

> have: logical self-consistency. E.g. rating systems should avoid

that

> double-counting (unless there is a reason to put a heavy weight on

> variable).

That's true and a good . I can add that to the routine speech I give

at work. Then when my people look at me funny, I can blame it on you.

I would phrase what you're talking about a little differently here,

though. A method makes assumptions at the start and those

assumptions should remain true at the end. Thinking off the top of

my head -- if Tendex assumes all those things to be worth one point,

shouldn't they all be worth one point at the end, too? Does this

mean Tendex should add up to points scored?

I know all the arguments pro and con with Tendex. I always point out

that Tendex, when applied to teams has only about a 70-80%

correlation with winning percentage. Which means it's not terribly

reliable for predicting winning teams and probably no more reliable

for predicting winning players. I also don't like the fact that it

really just encourages a lot of shooting. I don't know how well

Tendex correlates with points scored. But unlike baseball, where

position players are pretty much responsible for offense and pitchers

for defense, basketball players are responsible for both. That's why

I try to keep offensive and defensive contributions separate for

individuals. Doug Steele has an offensive and defensive Tendex

rating based on some conversations we had in '94. It was a start.

DeanO