OZDOC1050 wrote:

Thanks For your help Jerry, I'm way past home work and have been helping out
in the
forums in some way for years but this one has me stuck
perhaps im to old, any way I see by you clue it has something to do with the
.05 p
but really all this stuff is Dutch to me, so if you could help out further
it would be great
regards
Pete


For a binomial random variable, mean = n*p; variance = n*p*(1-p). The
general form of a z-test is
(x - mu(x)) / sigma(x)
where the standard deviation, sigma, is the square root of the variance.

The Excel worksheet function ZTEST looks different because it takes x to
be a sample average, but its sigma argument is the standard deviation of
a single observation, not the standard deviation of of the average,
hence the extra sqrt(n) factor.

You can save typing by using the fact that
NORMSDIST(x) = NORMDIST(x,1,0,TRUE)

Jerry