Again referring to (3.28), suppose now that Y = 3X 1 without error, but X 1 and X 2 are not perfectly correlated. Describe the appearance of the added-variable plot for X 2 after X 1 . Under what...

Again referring to (3.28), suppose now that Y = 3X₁
without error, but X₁
and X₂
are not perfectly correlated. Describe the appearance of the added-variable plot for X₂
after X₁.

Under what conditions will the added-variable plot for X₂
after X₁
have exactly the same shape as the marginal plot of Y versus X₂?

True or false: The vertical variation of the points in in an added variable plot for X₂
after X₁
is always less than or equal to the vertical variation in a plot of Y versus X₂. Explain.