The confidence interval for an individual regression parameter is given by $\hat \beta_j \pm t_{\alpha/2, \ n - (p + 1)} \sqrt{\hat \sigma^2 \Big [ (X^TX)^{-1}}\Big ]_{jj}$ In [[R]], `confint` will produce confidence intervals at the 95% confidence level. ```R confint(lm_model, level=0.95) ```