\[t - distribution,When{rm{ }}variance{rm{ }}is{rm{ }}unknown,{rm{ }}x = \frac{{{t_{\alpha /2}}s}}{{\surd n}}\]
\[t - distribution,When{\text{ }}variance{\text{ }}is{\text{ }}unknown,{\text{ }}x = \frac{{{t_{\alpha /2}}\sigma }}{{\surd n}}\]
Where: