Chapter 5. The Two-Sample t-Test
5.1 Introduction 67
5.2 Synopsis 67
5.3 Examples 68
5.4 Details & Notes 73
5.1 Introduction
The two-sample t-test is used to compare the means of two independent populations, denoted μ1 and μ2. This test has ubiquitous application in the analysis of controlled clinical trials. Examples might include the comparison of mean decreases in diastolic blood pressure between two groups of patients receiving different antihypertensive agents, or estimating pain relief from a new treatment relative to that of a placebo based on subjective assessment of percent-improvement in two parallel groups.
Assume that the two populations are normally distributed. If the variances are known, you can use a Z-test. However, in most cases, you ...
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