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Standard Deviation in Rankings

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Postby JDD » Wed Dec 29, 2004 4:56 pm

Use fantasy points instead of dollar amounts, and you will be on to something.

And factor in the 2002 and 2003 seasons as well, and put more weight on 2004.
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Postby shortsavage » Sun Jan 02, 2005 6:57 am

Looking at the SD values that I have come up with so far, Closer and Catcher are two of the positions with the least variation.

In the past, my gut has always told me to go with a bargain C or RP because they are a dime a dozen. A significant discovery, my values show 2B as being similarly close together for the 2005 season.

With Alfonzo Soriano's play dropping and Michael Young loosing 2B eligibility, this may be the year to pass on a "top 2B" and settle for a decent one (ex. Chone Figgins).
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Postby mbuser » Mon Jan 03, 2005 2:07 am

just curious how you guys use StDev to figure batting average (BA) value. my formula is as follows:

((players BA - league total BA)/BA StDev)*(player AB's/league average AB's)

replace league with position specific #'s to figure positional value. is there another way or are you guys using the same formula? even though i seem to be getting good numbers with that formula, what i'm really wondering if you can get a true StDev value for simple .XXX BA numbers or is there another way to figure it that would factor in AB's and result in a 'truer' number?
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Postby Cornbread Maxwell » Mon Jan 03, 2005 10:07 am

Maybe one of you guys can help me out, but as I noted before, I am not sure SD is a good measure for some things. Specifically, is SD a good measure when the sample size is not a normal bell curve?

Can you fellas tell me if I am wrong here?

If you have 4-6 players of similar value at the high end of the range, then 10-12 with a significant drop afterward, wouldnt the mean by which the SD is derived be completely irrelevant?
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Postby RugbyD » Mon Jan 03, 2005 11:28 am

Cornbread Maxwell wrote:Maybe one of you guys can help me out, but as I noted before, I am not sure SD is a good measure for some things. Specifically, is SD a good measure when the sample size is not a normal bell curve?

Can you fellas tell me if I am wrong here?

If you have 4-6 players of similar value at the high end of the range, then 10-12 with a significant drop afterward, wouldnt the mean by which the SD is derived be completely irrelevant?


You'd like to have a sample size of 30+ to begin with. I haven't run any devs yet but it wouldn't surprise me if some came out in a skewed/lognormal distribution because there are no negative raw value numbers. A double hump might pop up as well, but that would just help in solidifying a VORP/tiered draft strategy for that position.
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Postby Cornbread Maxwell » Mon Jan 03, 2005 12:17 pm

RugbyD wrote:
Cornbread Maxwell wrote:Maybe one of you guys can help me out, but as I noted before, I am not sure SD is a good measure for some things. Specifically, is SD a good measure when the sample size is not a normal bell curve?

Can you fellas tell me if I am wrong here?

If you have 4-6 players of similar value at the high end of the range, then 10-12 with a significant drop afterward, wouldnt the mean by which the SD is derived be completely irrelevant?


You'd like to have a sample size of 30+ to begin with. I haven't run any devs yet but it wouldn't surprise me if some came out in a skewed/lognormal distribution because there are no negative raw value numbers. A double hump might pop up as well, but that would just help in solidifying a VORP/tiered draft strategy for that position.


I guess thats my point - if you need to use a sample size of at least 30 then what you are doing is taking all of the starting players in baseball for a certain position - of course this wouldnt be a wise thing to do since in fantasy rarely do you go over the top 15-20 unless you are in a very deep league. Since the sample size is so small, and what you are essentially trying to do is rate the top half of each position, than bell curve calculations (stan. dev.) becomes a bit obsolete. That is why I would endorse a tiered system over using stand dev.
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Postby Amazinz » Mon Jan 03, 2005 12:26 pm

Definitely agree, Cornbread.

I just use a system similar to VBD where I will choose a baseline player based on how many I think will be drafted at that position. Then I rate players using their % above or below that baseline.
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Postby RugbyD » Mon Jan 03, 2005 12:30 pm

Cornbread Maxwell wrote:I guess thats my point - if you need to use a sample size of at least 30 then what you are doing is taking all of the starting players in baseball for a certain position - of course this wouldnt be a wise thing to do since in fantasy rarely do you go over the top 15-20 unless you are in a very deep league. Since the sample size is so small, and what you are essentially trying to do is rate the top half of each position, than bell curve calculations (stan. dev.) becomes a bit obsolete. That is why I would endorse a tiered system over using stand dev.


30+ is ideal, but 15-20 will do. Using std.dev is essentially the same as using tiers because all a tier is is a specific range if std.devs from the mean. The distribution just helps establish the appropriate tiers. The 1B/DH, OF, SP and MR distributions would paint the prettiest pictures of course.
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Postby Cornbread Maxwell » Mon Jan 03, 2005 12:47 pm

RugbyD wrote:30+ is ideal, but 15-20 will do. Using std.dev is essentially the same as using tiers because all a tier is is a specific range if std.devs from the mean. The distribution just helps establish the appropriate tiers. The 1B/DH, OF, SP and MR distributions would paint the prettiest pictures of course.


I understand thats what using SD is trying to do: 1 out from the mean, 2 out from the mean, etc... but the problem is that SD is based on a normal bell curve, and I argue that with a sample size of 15-20 of the best players at a position, there is rarely going to be a normal bell curve. Thats the whole argument. Therefore rather than using SD as a strict formula to determine tiers, I think there is probably a better way that a strict formula base would more than likely hinder.

I also want to add that a tiered approach is only based on SD - but it isnt locked into the strictness of it. Using a tiered approach and using a SD approach are not the same thing.
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Postby Amazinz » Mon Jan 03, 2005 1:00 pm

Cornbread Maxwell wrote:but the problem is that SD is based on a normal bell curve, and I argue that with a sample size of 15-20 of the best players at a position, there is rarely going to be a normal bell curve.

This is correct. Ideally you would use a T-Distribution.
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