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Section 21.4 Summary of Procedures for Paired Differences

Test of \(H_0: \mu_d = 0\).

Randomization test (randomizing the sign of the difference)
Paired t-test (Valid with \(n > 30\) or normal population of differences)
Standardized (test) statistic:
\begin{equation*} t_0 = \frac{\bar{x}_{diff} - \mu_0}{s_{diff}/\sqrt{n}} \end{equation*}
Degrees of freedom = \(n - 1\)

t-Confidence interval for \(\mu_d\).

\begin{equation*} \bar{x}_{diff} \pm t_{n-1}^* \times \frac{s_{diff}}{\sqrt{n}} \end{equation*}
Valid with \(n > 30\) or normal population of differences
The paired t-test is equivalent to a one-sample t-test on the differences. Also keep in mind that even if the original distributions are skewed, the differences could still be more normally distributed.
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