Math Topic: Can standard deviations include values with different weights?

[blademan88]

Hi all,
I know this is a excel board and not a math board but I'm not sure where to ask this and everyone was very helpful on last question. Anyhow, I figure you guys have run into this before dealing with excel...

I am trying to calculate the effect a basketball players FG% on his teams FG%. The problem is that I need the players effect in standard deviation if possible yet am not sure how to incorporate weight (how many times they shoot). I have the data for shots made and attempted for each player on the team. I tried all last night dealing with different variations of standard deviation to get something accurate but think I've failed so far.

Thanks,
Ori

Just to clarify, I know how to use stdev well, its just I dont know how to do this specifically.

 

[GeofW]

Ori,

I played around with this. I don't have the add-in so I'll describe what I set up in the worksheet. I used 4 players. In Column A, rows 2-5 I had p1 to p4.
Column B # field goals, say 10, 12, 8, 11
Column C # attempts say, 15, 17, 15, 16
Cell B6 had the total 41 fgs, cell C6 had the total attempts 62, cell D6 had the team average = 41/62 = 10.25
Column E had the observation - the average, eg =B2-$D$6 for row 2.
Column F had the square of the deviation from the mean, eg =E2^2 for row 2.
cell F6 had the sum of the square of the deviations from the mean, which is the numerator for the variance.
So you can see how a player's # fgs affects the std dev by altering one or more column B values. But there's not much you can do with the number of shots they take.