Interpretation of graphs, the first graph had perpendicular lines from the error to the fitted line and the second graph had lines from the error to the fitted line, parallel to the y-axis. - Interpreted the first graph as implementation of OLS using projection matrices (solving nearest possible solution for Ax=b by solving Ax'=b') and second as evaluation of linear regression to any y-pred - y-actual method. The interviewer wasn't aware of projections matrices and was expected PCA as answer