3. Model assumption: 1.E()=0 2. E(Ge=oI,(I, is a unit matrix) 3. Xis non-random 4. rank(X)=k+l< n 5. Normality assumption E~N(0,o2)(i=1,…,n)3. Model assumption: 1. 2. 3. is non-random. 4. 5. Normality assumption E( ) ε = 0 2 E( ) ( is a unit matrix)  n n εε = I I X rank( )= 1 X k n +  2 (0, ) ( 1, , )   i N i n =