DM: Quinlan's formular

[kim hyunjoo]

Dear colleagues,

I have a question on how to calculate Quinlan's formular, predicted 
error rate of 

U  (E,N)
 CF

(CF is confidence level, N training cases, and E resubstitution error
rate)

He said in page 41 of his book, "C4.5 Programs for machine learning" 
that 

U   (0,6) = 0.206.
 25%

I do not know how he got this number.

Please help me.

Thank you,

Hyun
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