Simple CIS Math With Joe Scanlon

Last season I did a column focusing on how a plus-minus system similar to
the one used in hockey might work for basketball. I did it by focusing on
two games and the players on one team in each of those games. The teams I
chose were Ottawa U and Queen’s. In both cases, their teams were playing
against Carleton.

This season I decided to try it again this time looking at the women’s teams
from Toronto and Ryerson, again when both were involved in a game against
Carleton. I was a little worried that Toronto might overpower Carleton and
make the results a bit meaningless. As it happened, the Ravens put a good
showing against the Blues. Though they trailed by 14 at half time they
managed to give up only two more points the rest of the way. They actually
were close to making a game of it in the fourth quarter before the Blues put
on a final rush. That forced Toronto coach Michele Belanger to keep a strong
line-up in the game. The Ryerson-Carleton was even tighter: Carleton came
back to win it in the final minute.

Before continuing, let me make clear that doing a plus-minus for basketball
is a lot more difficult than for hockey. In hockey, especially today,
players go on and off the ice in sort shifts. No player plays the entire
game. In basketball, it is not uncommon for someone to play 30+ minutes,
sometimes almost the entire game. As a result their plus-minus is really
just the result of the team’s overall performance. If their team wins that
player comes up with a plus. If the team loses that same player will have a
minus.

Another problem is that there is a lot more scoring in basketball than
hockey so raw +/- figures are enormous. At the moment, for example, Jennifer
Donofrio of RMC is averaging 20 points a game but RMC is losing all of its
games mainly by a large margin. Since she plays on average 34 minutes per
game and RMC loses on average by 36 points her raw +/- would be 34/40 of -36
or -31, not much to write home about. In contrast, Lindsay de Groot average
17.6 points a game for undefeated McMaster and plays 27 minutes per game.
McMaster wins on average by 26 points. Her raw +/- figure would be 27/40 of
26 or +17.5. On that basis, it sounds as if de Groot is far more valuable
than Donofrio.

It’s also not all that easy to keep track of whose is on the floor when
points are scored. Unlike hockey where goals usually come minutes or even
periods apart, in basketball there can be a lot of scoring. It takes a lot
of concentration to keep track of who is on the floor for every point.
Despite those limitations, I argued last season and will do so again that
+/- could be a useful tool for CIS coaches.

The system I have used was developed by Wayne Winston is a former Jeopardy
champion who is also a Professor of Decision Sciences at Indiana University.
Along with Jeff Sagarin, the brains behind the rankings in USA Today,
Winston created Winval. It does – for basketball – what +/- does for hockey
— shows if a team does better when a particular player is on the floor and
worse when he or she is not playing. It also adjusts for comparative team
strength and strengths of other players when someone is on the floor.

What I did was take this concept and simplify it. While watching a game, I
compile the raw statistics – the difference between points for and against
when a player is on floor. (I charge points scored on foul shots to players
who were on the floor when the foul occurred.) Then I divide that raw +/- by
the minutes played. I compare that to a team’s adjusted +/-.

Here’s how it works. If Jones played 30 minutes for Team A and his team
outscored their opponents by 25 points while he was on the floor, his
average per minute played would be +.83 (25 divided by 30). If Team A
defeats Team B by 40 Points the team average per minute would be +1 (40
points more than the other team in 40 minutes). With the team average +1 and
Jones at+.83 clearly the team did better when Jones was not playing. His 25
points look less impressive when +/- is calculated. To make that clear his
team outscored its opponent by 15 points during the 10 minutes he was not
playing. That’s a rate of 1.5 points a minute, a better rate that when Jones
was on the floor.

Incidentally, any player can have an off night or on night so statistics
based on one game have to be looked at with caution. It’s also possible a
player is coming off an injury and the coach has made allowances for that.
But it would seem to me that a perceptive coach would pay attention to those
things and that a player having a good night would get extra floor time and
one having a bad night would get less floor time.

Toronto defeated Carleton 55-39, winning by 16 points. Their raw plus-minus
was +16. The team’s adjusted +/- is 16 divided by 40 or .4. If a player was
on for the entire game her plus-minus would be the team +/- in short also
.4. However, no one did that so one can take the raw +/- for each player,
divide it by the number of minutes played and see how that player compares
to the team norm.

First, let’s look at Toronto’s raw +/- statistics; and look at them in
order.

Kyla Burwash + 17, Jessica Hieuw + 17, Amanda Van Leeuwen + 17, Alaine
Hutton + 15, Christine Cho + 12, Ilana Weissberger + 11, Lyndsay Cloughley
+1, Laila Bellony -6, Erin Mc Neely -3, Sherri Pierce – 1. This total adds
up to 80 which divided by five gives the team margin of 16 points.

Clearly, the figures for Bellony, McNeely and Pierce show they were not
having a great night. Toronto won by 16 but was outscored by Carleton when
those three were on the floor. It would also appear that Burwash, Hieuw and
Leeuwen had good games since they had a + figure better than the team’s
winning margin of 16 points. However, those figures change somewhat when
they are adjusted by minutes played.

Toronto was +17 when Van Leeuwen was on the floor but she played only 17
minutes, far fewer than Burwash and Hieuw. Van Leeuwen’s adjusted plus-minus
was 1.0, two and a half times as good as the team average. Burwash was .62
and Hieuw, who had one more minute than Burwash, .61, both better than the
team’s average. Hutton however also played 28 minutes, the same as Hieuw but
had a lower raw figure. She is at .53 still better than the team’s average.
The other really good performance was by Ilana Weissberger who was +.79.
Alaine Hutton was +.53, also better than the team average. Christie Cho was
.67. All in all then Toronto’s starters were the best players on the floor
and the coach was correct – based on these figures – to give them the
playing time she did. I have not worked the adjusted figures for the three
players whose raw figures were in the minus column. Clearly they did not
have a good night. Except by Bellony, those three got little playing in the
second half.

Overall, I would conclude that the most part Michele Belanger was making
good decisions about who should be playing – as one would hope.

The second game I looked at was the Ryerson game against Carleton the
following night. The Rams lead from the opening whistle but Carleton came on
strong in the closing minutes outscoring Ryerson by 10 in the last quarter.

Since Ryerson lost by three, 55-52, the team’s raw plus-minus is -.075. The
fact that the figure is negative does not matter. The question remains: how
did a player do compared to the team?

For Ryerson the raw +/- figures were as follows: Kaitlyn Taylor + 13;
Rebecca Cox +7; Lisa Goldring +5; Gwen Elliot -2; Lacey O’Sullivan – 5;
Ashley MacDonald – 8; Tanya LeClerc – 13; Lindsay Taylor – 14.

At first glance, that would suggest that Taylor, Cox and Goldring were the
best players on the floor but it is not quite that simple Gwen Elliot played
only seven minutes. Her adjusted +/- is .28 far worse than the team’s
average. Ashley MacDonald (-.6) who played 13 minutes is not nearly as bad
as Lindsay Taylor who played only six minutes all in the first half when
Ryerson was winning and still managed an adjusted -2.3, a very high figure.
It means that although Ryerson was up at half time, it trailed by an average
2.3 points while Taylor was on the floor. It is not surprising she did not
get back on during the second half.

What about Kaitlyn Taylor, Cox and Goldring, the three players were + raw
figures?

Taylor was +.39. Cox was+ .18. Goldring was +.13. Except for Kaitlyn Taylor
their raw figures are deceptive. They were an asset but not as much of an
asset as the raw figures would suggest.

Experience tells me most coaches don’t trust +/-. They don’t want a
statistic that might suggest their best scorers are not an asset overall.
But I think +/- adds something to a coach’s awareness of what a player
contributes to the team and other players on that team.

I think most coaches know what is happening without the need to look at +/-.
But I also think it is a useful tool for post-game analysis and for seeing
if a player’s good scoring record actually contributes to the team’s
success. It s also possible to take a look at the figures on any given night
to see who is having an on night or an off night.

Take, for example, a look at the six players Sandra Pothier used during the
closing minutes as Ryerson watched its lead slip away. They were O’Sullivan,
Goldring, Cox, Kaitlyn Taylor, Jenny Hobbs and finally Tanya LeClerc. Cox,
Taylor and Goldring make sense as does Jenny Hobbs. They still ended up in
the plus column even though they were on when Carleton made its comeback.
O’Sullivan would have looked like a good choice: she was ahead on +/- until
Carleton made its final run. LeClerc was a more doubtful choice. A look at
the detailed+/- records show Carleton outscored Ryerson every time she was
on the floor during the entire game.

The point of this column was not to pick apart a player’s or coaches’
performance on a particular night. It was to give a little insight into how
+/- might work and suggest it might be a useful tool for coaches who wish to
look back at a game to see how well tuned in they were to how particular
players were doing.