Residual Plot

Question 1

What are properties f a residual plot?

Answer 1

• Scatterplot of regression residuals (Y) against explanatory variable X
• Helps assessing the fit of regression line
• Shows deviations and outliers
• If random: linear regression is appropriate
• If Non-random: It doesn’t make sense to use
linear regression!

Question 2

Random and Non-Random

Answer 2

Random: the residuals are spread around the 0 line as a random cloud
Non-random: the residuals are organized in some sort of pattern around the 0 line
(eg curvilinear correlations)

Question 3

Exam question
Which statement is correct?
I. The sum of all residuals equals always 0.
II. The steeper the slope of the regression line, the bigger the correlation.

A. Both I and II are false
B. Only I is correct
C. Only II is correct
D. Both I and II are correct

Answer 3

Answer B