In linear regression dignostics, how do we tell if the constant variance assumption hold?

(1) By inspecting the residuals vs fitted values plot to see if the points are randomly scattered.

(2) By conducting an ANOVA analysis on the residuals.

(3) By inspecting the residuals vs fitted values plot to see if the points are close to the diagonal line.

(4) By plotting the residuals and see if it is close to a bell curve.

In linear regression dignostics, how do we tell if there are influential outliers or not?

(1) By inspecting the cook's distance plot to see if the points are randomly scattered.

(2) By inspecting the residuals vs fitted values plot to see if the points are randomly scattered.

(3) By inspecting the residuals vs fitted values plot to see if the points are more or less on the diagonal line.

(4) y inspecting the cook's distance plot to see if there are points beyond the dotted curves.

(5) By plotting the residuals and see if it is close to a bell curve.