8 The Difference Between Two Means

Overview

Are the mean responses from two groups different? What evidence would it take to convince you? This question opens the door to many of the issues that pervade statistical inference, and this chapter explores these issues. Comparing group means also introduces an important statistical distinction regarding how the measurement or sampling process affects the way the resulting data are analyzed. This chapter also talks about validating statistical assumptions.

When two groups are considered, there are two distinct situations that lead to two different analyses:

Independent Groups—the responses from the two groups are unrelated and statistically independent. For example, the two groups might be two classrooms ...

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