9.3 Regression on a Quantitative Variable and a Qualitative Variable with More Than Two Classes or Categories--Introduce m-1 dummy variables ●1. Model: Y1=B1+B2D21+B3D31+B4X1+u E(YID2 =0D3=0X =B+B4X (9.14 E(YD2=1D3=0X)=(B1+B2)+B4 (9.15) E(YD2=0D3=1X)(B1+B3)+B4x1 (9.16) ●2. Estimate9.3 Regression on a Quantitative Variable and a Qualitative Variable with More Than Two Classes or Categories——Introduce m－1 dummy variables ⚫ 1. Model: Yi = B1+B2D2i +B3 D3i +B4Xi +ui (9.13) E(Yi |D2 =0′D3 =0′Xi )=B1+B4Xi (9.14) E(Yi |D2 =1′D3 =0′Xi )=(B1+B2 )+B4Xi (9.15) E(Yi |D2 =0′D3 =1′Xi )=(B1+B3 )+B4Xi (9.16) ⚫ 2. Estimate