Suppose that the "true" model is but we add an "irrelevant" variable X3 to the model (irrelevant in the sense that the true coefficient attached to the variable X3 is zero) and estimate
a. Would the R2 and the adjusted R2 for model (2) be larger than that for model (1)?
b. Are the estimates ofand obtained from (2) unbiased?
c. Does the inclusion of the "irrelevant" variable X3 affect the variancesof and?