13.2 Types of Specification Errors 1. Omitting a Relevant Variable: Underfitting or "Underspecifying"a Model True model:Yt=B1+B2×2+B3×3t+pt(13.1) Misspecified model:Y =A1+A2X2t+ut(13.2)13.2 Types of Specification Errors 1.Omitting a Relevant Variable: “Underfitting” or “Underspecifying” a Model True model: Yt=B1+B2X2t+B3X3t+μt (13.1) Misspecified model: Yt=A1+A2X2t+μt (13.2)