formula

$\overline{X}_n\equiv\frac{1}{n}\sum^n_{i=1}X_i, \quad \tilde{\sigma}^2_n\equiv\frac{1}{n-1}\sum^n_{i=1}(X_i - \overline{X}_n)^2\\ T_s\equiv\displaystyle\frac{\sqrt{n}(\overline{X}_n - \mu)}{\tilde{\sigma}_n} \\$