요약

\begin{eqnarray} z\;\;\;\text{or}\;\;\;t = \frac{\overline{X}-\mu}{\sigma_{\overline{X}} } \\ t = \frac{\overline{X}-\mu}{s_{\overline{X}} } \\ t = \frac{(\overline{X_a}-\overline{X_b})-(\mu_a-\mu_b)}{\sigma_{diff}} \\ t = \frac{\overline{D}-0}{s_{ \overline{D} }} = \frac {\overline{D}}{ \frac{s_D}{\sqrt{N}} } \end{eqnarray}