Introduction
In this lesson, we’ll continue our investigation of hypothesis testing. In this case, we’ll focus our attention on a hypothesis test for the difference in two population meansμ1μ2for two situations:
ahypothesis test based on thet-distribution, known as thepooled two-samplet-test, forμ1μ2when the (unknown) population variancesandare equala hypothesis test based on thet-distribution, known asWelch’st-test, forμ1μ2when the (unknown) population variancesandare not equal
Of course, because population variances are generally not known, there is no way of being 100% sure that the population variances are equal or not equal. In order to be able to determine, therefore, which of the two hypothesis tests we should use, we’ll need to make some assumptions about the equality of the variances based on our previous knowledge of the populations we’re studying.
link：When Population Variances Are EqualWhen Population Variances Are Not EqualUsing Minitab
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