## Function Confidence-Interval-Z

(

**confidence-interval-z** &rest < args > )

confidence-interval-z (data confidence)

Suppose you have a sample of 50 numbers and you want to compute a 90 percent

confidence interval on the population mean. This function is the one to use.

Note that it makes the assumption that the sampling distribution is normal, so

it's inappropriate for small sample sizes. Use confidence-interval-t instead.

It returns three values: the mean and the lower and upper bound of the

confidence interval. True, only two numbers are necessary, but the confidence

intervals of other statistics may be asymmetrical and these values would be

consistent with those confidence intervals. This function handles 90, 95 and 99

percent confidence intervals as special cases, so those will be quite fast.

` Sample' should be a sequence of numbers. `

Confidence' should be a number

between 0 and 1, exclusive.