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 alternative
mean (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.
Package: statistics