Confidence intervals in multivariate linear regression
Looking at https://en.wikipedia.org/wiki/Simple_linear_regression :

This t-value has a Student's t-distribution with $n-2$ degrees of freedom. Using it we can construct a confidence interval for $\beta$:

$$ \beta \in \left[\widehat\beta - s_{\widehat\beta} t^*_{n - 2},\ \widehat\beta + s_{\widehat\beta} t^*_{n - 2}\right] $$

at confidence level $1-\gamma$, where $t^*_{n - 2}$ is the $(1-\frac{\gamma}{2})$-th quantile of the $t_{n−2}$ distribution.