docs: result in manual degrees of freedom calculation (Statistics)

Author: JakobKlotz

docs/statistics/hypothesis/Ttest.md

@@ -598,7 +598,7 @@ The **two-sample t-test**, also known as the **independent samples t-test**, is
         - **Determine degrees of freedom (df)** using Welch's formula:
 
             \[
-            df = \frac{\left( \frac{s_1^2}{n_1} + \frac{s_2^2}{n_2} \right)^2}{\frac{\left( \frac{s_1^2}{n_1} \right)^2}{n_1 - 1} + \frac{\left( \frac{s_2^2}{n_2} \right)^2}{n_2 - 1}} \approx 57.31
+            df = \frac{\left( \frac{s_1^2}{n_1} + \frac{s_2^2}{n_2} \right)^2}{\frac{\left( \frac{s_1^2}{n_1} \right)^2}{n_1 - 1} + \frac{\left( \frac{s_2^2}{n_2} \right)^2}{n_2 - 1}} \approx 62.91
             \]
 
             ```py