The Regression Equation for a Categorical Variable with Four Categories

The regression equation for a categorical variable with four categories would be modeled as .

A) Y^{^} = b₁ D_{1 +} b₂ D_{2 +} b₃D_{3 +} b₄D₄
B) Y^{^} = b₁ D_{1 +} b₂ D_{2 +} b₃D₃
C) Y^{^} _i = a + b₁ D_{1 +} b₂ D_{2 +} b₃D_{3 +} b₄D₄
D) Y^{^} _i = a + b₁ D_{1 +} b₂ D_{2 +} b₃D₃