For two samples x and y from normal distributions with unknown means and unknown and not necessarily equal variances, perform a Welch test of the null hypothesis of equal means. Under the null, the test statistic t approximately follows a Student distribution with df degrees of freedom.
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 alternativemean (
x) !=
m. If alt is">"
, the one-sided alternative mean(x) > m is considered. Similarly for"<"
, the one-sided alternative mean(x) < m is considered. 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.