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confidence interval (fwd)
Posted:
Jan 3, 1997 8:00 PM


 Forwarded message from Jenny Kotlerman 
In Moore's Basic Statistics book, on page 327 at the bottom, it says: " so in 95% of all samples the unknown mu lies between x4.2 and x+4.2" where x is the known sample mean and mu is the unknown population mean. This statement does not seem to make sense to me.
I think it's right. You have to think of x as a varaiable that may change from sample to sample. Each sample has a (possibly different) CI associated with it. 95% of these include mu.
I thought that it should say "95% of all samples should contain the unknown mean of the population, mu."
I'm not sure what this means. Does the sample {12,14,21,8,11} "contain" the population mean if mu=13?
or " we are 95% confident that the mean of the population will lie between x4.2 and x+4.2"
That's OK if you have already defined "95% confident".
It seems that the statement given in the book says that 95% of the samples will have a population mean in that interval and the other 5% will have the population mean somewhere else. How can that be?
Again, it's not "that interval" but "those intervalS".
 End of forwarded message from Jenny Kotlerman 

_   Robert W. Hayden   Department of Mathematics /  Plymouth State College MSC#29   Plymouth, New Hampshire 03264 USA  *  Rural Route 1, Box 10 /  Ashland, NH 032179702  ) (603) 9689914 (home) L_____/ hayden@oz.plymouth.edu fax (603) 5352943 (work)



