Question

When conducting a residual analysis, which plot would you look at to determine if the normal assumption is satisfied?

  

Scatter Plot of Residuals vs QN X

   

Scatter Plot of Residuals vs Yhat

   

Scatter plot of Yhat vs. QN X

   

Stem-and-Leaf Plot of the Zresiduals

NOTE: Answer is NOT Scatter Plot of Residuals vs Yhat

Answer 1

In regression analysis, we assume that the underlying distribution is normal. That is, the residuals , this also follows the assumption of homoscedasticity.

If we want to determine if the normal assumption is satisfied, we want to plot the residuals as an histogram, and check if the histogram looks like a normal distribution. A stem and leaf plot allows us to look at the data in a similar way as a histogram would. If we create a stem and leaf plot of the Z-residuals and see that it is symmetric about zero, then the normally assumption would be fulfilled. Hence, the fourth option is the correct option.