T-test for Two Independent Samples in Stata (Two-sample T-test)

This video clearly explains how to perform a two-sample t-test in Stata. The two-sample t-test is done when we want to compare the means of two groups from two different populations. In this video, we compare the bp_before means of male and female groups.
Our null hypothesis is that the difference is zero (diff = 0).
I) In the case of a one-tailed t-test, the alternative hypothesis is: the difference is not equal to zero (diff != 0)
II) In the case of a two-tailed t-test, the alternative hypothesis: the difference is greater than zero or the difference is less than zero