2.3 For Model (2.7) for the data on birthweight and gestational age, using methods similar to those for Exercise 1.4, show Sb1 =

J

∑

j=1 K

∑

k=1

(Yjk −aj −bjxjk)

2

=

J

∑

j=1 K

∑

k=1

(Yjk −(αj +βjxjk)

2 −K J

∑

j=1

(Y j −αj −βjx j)

2

−

J

∑

j=1

(bj −βj)

2

(

K

∑

k=1 x

2 jk −Kx 2

j