ZvP is imbalanced - Page 34

On October 21 2009 01:43 zulu_nation8 wrote:
can you explain to me why 1-P0 is the SD

On October 21 2009 01:14 zulu_nation8 wrote:


motbob i think its pretty obvious a standard deviation of 50% is wrong, the sooner you realize this and drop the im an econ major i know stats attitude, the faster we can move on.

A win is not 100%, and a loss is not 0%, that would be the standard deviation if brood war had like 80% half wins or something, even then that would not make sense since there would be no statistical significance since EVERYTHING would fall under the range of 0 and 1, thats why your numbers are so messed up.

On October 21 2009 02:03 JWD wrote:
motbob I'm going to try to explain exactly why your standard deviation (technically it's a standard error, since standard deviation is a "true", unascertainable value and we are just estimating it) is wrong, since zulu won't do it. I think what you did is to calculate the standard error of the variable zerg win, which is a binary variable you defined (I picked the name for exposition's sake) that equals 1 if Zerg wins a ZvP and 0 if Protoss wins. You correctly calculated the standard error of this variable — we'd expect it to be near .5 because the mean of zerg win is about .5, and so each instance of zerg win is about .5 from that mean.

However, this standard error is not the standard error relevant to your test for determining whether the recent Z>P trend is significantly anomalous. The variable you are examining in that test is not zerg win, but ZvP balance over a several-month period, another variable which I'll call balance. Therefore the standard error you must use in your test is the standard error of balance—that is, the error of several-month ZvP balance from the mean several-month ZvP balance. You can NOT use the standard error of zerg win, which has no place in your calculation.

On October 21 2009 02:03 motbob wrote:

You are making a fool out of yourself. Stop trying to pretend you know more about stats than me. You're tripped over your terminology and your methodology ever since we started having this discussion. You continually make basic mistakes like confusing standard deviation with standard error. I'm going to say it again: either do a statistical test of your own or stop trying to criticize my methods.

On October 21 2009 02:11 Black Gun wrote:



u should read my last 2 posts. in the first one i conducted the correct tests. in the second one i explained in detail why the standard error i was using is the correct one. and no, it is not hard to compute the sd of "balance". once we get a certain zvp winning percentage as the "historical balance", the sd needed in our test is simply sqrt[p*(1-p)/n]. i already tried it with 55%, so if the historical zvp stats are not higher than 55%, then the outcome of the last 7 months differs significantly.



im a statistics major close to graduating, so u can believe me

On October 21 2009 02:12 zulu_nation8 wrote:


first of all motbob, i think you should calm down. I learned this stuff in a psych 101 class 3 years ago so I assume it's pretty basic stuff and nothing to get worked up about. You plugged in .49 for standard deviation, not standard deviation, SE = SD/root(885). I had no idea how you got the number but just by common sense you should see that a SD of 50% for a null of 50% is wrong. I plan to do the test when I get access to TLPD. But you really should calm down or else this will go nowhere.

On October 21 2009 02:16 motbob wrote:

dude

it's binary data, the data points are either a 1 or 0. Of course the stdev is going to be ~.5! Punch a bunch of binary data into excel and use excel to get the stdev of that data. It will give you a value of about .5

On October 21 2009 02:03 JWD wrote:
motbob I'm going to try to explain exactly why your standard deviation (technically it's a standard error, since standard deviation is a "true", unascertainable value and we are just estimating it) is wrong, since zulu won't do it. I think what you did is to calculate the standard error of the variable zerg win, which is a binary variable you defined (I picked the name for exposition's sake) that equals 1 if Zerg wins a ZvP and 0 if Protoss wins. You correctly calculated the standard error of this variable — we'd expect it to be near .5 because the mean of zerg win is about .5, and so each instance of zerg win is about .5 from that mean.

However, this standard error is not the standard error relevant to your test for determining whether the recent Z>P trend is significantly anomalous. The variable you are examining in that test is not zerg win, but ZvP balance over a several-month period, another variable which I'll call balance. Therefore the standard error you must use in your test is the standard error of balance—that is, the error of several-month ZvP balance from the mean several-month ZvP balance. You can NOT use the standard error of zerg win, which has no place in your calculation.

On October 21 2009 02:18 motbob wrote:

...I don't have a choice as to which SE I use in my test. SE is SD (of my data) divided by sqrt(n). I can't change it.

I can change my null hypothesis though... are you saying my null hypothesis should be the historical winrate instead of 50%?

On October 21 2009 02:11 Black Gun wrote:



u should read my last 2 posts. in the first one i conducted the correct tests. in the second one i explained in detail why the standard error i was using is the correct one. and no, it is not hard to compute the sd of "balance". once we get a certain zvp winning percentage as the "historical balance", the sd needed in our test is simply sqrt[p*(1-p)/n]. i already tried it with 55%, so if the historical zvp stats are not higher than 55%, then the outcome of the last 7 months differs significantly.



im a statistics major close to graduating, so u can believe me

On October 21 2009 02:19 JWD wrote:

yeah I confused standard error and stdev, and just edited to fix that…no that's not what I'm saying.

I'm too rusty on stats to make any further useful contributions to this thread, but I'm pretty sure I explained your problem right motbob