Consider the Following Partial Computer Output for a Multiple Regression

Consider the following partial computer output for a multiple regression model. $\begin{array} { l l l } \text { Predictor } & \text { Coefficient } \left( \mathrm { b } _ { \mathrm { i } } \right) & \text { Standard Dev } \left( \mathrm { s } _ { \mathrm { b } } \right) \\\text { Constant } & 99.3883 & \\\text { X1 } & - 0.007207 & 0.0031 \\\mathrm { X } 2 & 0.0011336 & 0.00122 \\\mathrm { X } 3 & 0.9324 & 0.373\end{array}$
The calculated value of the t statistic for X1 is ________.