Dropping Irrelevant Variables from a Regression Equation Might Provide a Better

Multiple Choice

Dropping irrelevant variables from a regression equation might provide a better regression in what sense?

A) Only when the irrelevant variables are uncorrelated with the treatment(s) .
B) Might facilitate more efficient/precise estimates of the treatment effect (smaller standard errors) .
C) Only if the irrelevant variables have low p-values.
D) Only if the irrelevant variables have many outliers.