Linear Regression & Residuals (Lecture 9)

Question 1

Variability - How do you calculate the residual?

Answer 1

Observed - Expected

Question 2

Variability - How do you calculate the model?

Answer 2

Expected - Mean

Question 3

What is SSE a measure of?

Answer 3

how well the regression fits the actual data

Question 4

What is SSM a measure of?

Answer 4

how different is the slope from zero

Question 5

Why is it significant when the y-intercept is not zero?

Answer 5

Generally indicates an error. For the bug mass vs wing area a y-intercept not equal to zero would indicate bugs were measured with no mass, but wings.

Question 6

What does one look for in a “Normal Q-Q” plot?

Answer 6

The residuals falling on a straight line. This indicated the residual come from a normal distribution. Normality.

Question 7

Describe a graph that displays homoscedasticity, and one that displays heteroscedasticity

Answer 7

homoscedasticity - residuals fluctuate uniformly around zero.
heteroscedasticity - residuals show fanning