[R] Question about statistics

Roy Werkman roy.werkman at asml.com
Wed Jul 6 11:00:27 CEST 2005


Although my question is not directly linked to R functionality, I hope
you can forgive me for posing it here. I have been looking for the
answer for a long time (~ 4 weeks) and have not been able to find it. My
question is:

Suppose I have an m*n matrix, with a random (normally distributed)
number per cell. Added to that I have a random number per column. I want
to determine the standard deviation of both distributions. For the
column-to-column (coco) sd I do following:

sd(coco) = sqrt(     sd(column averages)^2 - C * sd(cece)^2 /m     )

Where C = (m*n-1) / (m*n-n) , and sd(cece) is the sd over the matrix
with the column averages subtracted.

My question: how can I calculate the confidence interval on sd(coco)?

I would really appreciate your help,
Roy Werkman

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