Derivation or source of the chisquare statistic for sample size

[tom325@sbcglobal.net]

Could someone point me to a derivation or the factor 2*(n+1) used for the degrees of freedom when using the chi-square distribution to estimate a sample size for a test? I ran across it once but have not been able to dig it up again.

Thanks.

[Pantelis RS]

Look for it in any textbook (reliability and/or statistics) dealing with the exponential distribution and confidence limits (with censoring).

If I recall correctly you can find this in:
Reliability and Life Testing Handbook, Vols 1 & 2, by Dimitri Kececioglu.

See http://www.reliasoft.com/Books/index.html