For two samples x and y from normal distributions with unknown means and known variances v_x and v_y, perform a Z-test of the hypothesis of equal means.
Under the null, the test statistic z follows a standard normal distribution.
With the optional argument string alt, the alternative of interest
can be selected. If alt is "!=" or "<>", the null
is tested against the two-sided alternative
mean (x) != mean (y). If alt is ">", the
one-sided alternative mean (x) > mean (y) is used.
Similarly for "<", the one-sided alternative
mean (x) < mean (y) is used. The default is the
two-sided case.
The p-value of the test is returned in pval.
If no output argument is given, the p-value of the test is displayed along with some information.
Package: statistics