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Topic: confidence interval (fwd)
Replies: 0

 Bob Hayden Posts: 2,384 Registered: 12/6/04
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 x-4.2 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
x-4.2 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 -----

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