corrected for underscores

Underscores "_" in defunct equations were replaced by "\_" to make them render correctly in in-line math.

Author: JoramSoch

P/ug-ttest2.md

@@ -94,7 +94,7 @@ $$ \label{eq:mean-samp-dist}
 \end{split}
 $$
 
-Again employing the linear combination theorem and applying the null hypothesis from \eqref{eq:ttest2-h0}, the distribution of $Z = ( ( \bar{y}_1 - \bar{y}_2 ) - \mu_{\Delta} ) / ( \sigma \sqrt{1/n_1+1/n_2} )$ becomes [standard normal](/D/snorm)
+Again employing the linear combination theorem and applying the null hypothesis from \eqref{eq:ttest2-h0}, the distribution of $Z = ((\bar{y}\_1-\bar{y}\_2) - \mu\_{\Delta}) / (\sigma \sqrt{1/n\_1+1/n\_2})$ becomes [standard normal](/D/snorm)
 
 $$ \label{eq:Z-dist}
 Z = \frac{(\bar{y}_1-\bar{y}_2)-\mu_\Delta}{\sigma \cdot \sqrt{\frac{1}{n_1}+\frac{1}{n_2}}} \sim \mathcal{N}\left( \frac{(\mu_1-\mu_2)-\mu_\Delta}{\sigma \cdot \sqrt{\frac{1}{n_1}+\frac{1}{n_2}}}, \left(\frac{1}{\sigma \cdot \sqrt{\frac{1}{n_1}+\frac{1}{n_2}}}\right)^2 \left( \frac{\sigma^2}{n_1} + \frac{\sigma^2}{n_2} \right) \right) \overset{H_0}{=} \mathcal{N}\left( 0, 1 \right) \; .