Bayesian ranking

Hi Experts,

Please refer to the web page http://en.wikipedia.org/wiki/TrueSkill

What I would like to know is what does the following mean?

"As such N(x) can be interpreted as the probability that the player's "true" skill is x."

If my Mu is 25 and my Sigma is 3 how are these values used in the above to give my skill?
DColinAsked:
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ozoCommented:
if your Mu is 25 and your Sigma is 3, then the probability that your true skill is between x0 and x1 is
(erf((x1-25)/(3sqrt2))-erf((x0-25)/(3sqrt2)))/2
e.g. there would be a 0.683 probability that your true skill is between 22 and 28
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DColinAuthor Commented:
Hi Ozo,

Thanks for your reply, I have some questions.

How do I calculate the error function?
What does 3sqrt2 mean?
Where do the values of X0 and X1 come from?
Can I work out the X0 and X1 values for a given probability of say 99%?
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ozoCommented:
See, for example, http://en.wikipedia.org/wiki/Normal_distribution
A 99% confidence interval would be about 2.6 sigma, or 25±7.7
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DColinAuthor Commented:
Hi Ozo,

What does 3sqrt2 mean?
How do I calculate erf?
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ozoCommented:
Sigma * square root of 2
Usually one would look up values in a table, or use one of the formulas referenced at links like the above.
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