`(z-test x-bar n #:mu #:sigma #:tails)`procedureGiven

`x-bar`the sample mean,`n`the number in the sample,`#:mu`the distribution mean (defaults to 0),`#:sigma`the distribution standard deviation (defaults to 1), and`#:tails`the significance to report on:`':both`, the probability of the difference between`x-bar`and`#:mu``':positive`, the probability that observation is`>= x-bar``':negative`, the probability that observation is`<= x-bar`

e.g. given a distribution with mean 50 and standard deviation 10

; probability that a single observation is <= 40 > (z-test 40 1 #:mu 50 #:sigma 10 #:tails ':negative) 0.158655 ; probability that 10 observations are <= 40 > (z-test 40 10 #:mu 50 #:sigma 10 #:tails ':negative) 0.000783 ; probability that 5 observations give a mean of 40 > (z-test 40 5 #:mu 50 #:sigma 10) 0.025347