Londonrocks

you raise a very good point. frankly i am not too sure about this either, but one way to look at this would be since the higher variance is used in the numerator one is effectively forcing the test statistic into the right tail which then is the relevant null rejection region for a "greater than" alternative hypothesis. the way its worded in the curriculum, it appears that the same test statistic / rejection region is used to reject the null for both the greater than and less than alternatives. as you point out, that really doesnt make sense.