The following data is on

X=Automobile Stock per capita,

P= Relative price of automobiles and

Id= Real disposable income per capita

Years

Xt

Pt

Idt

Years

Xt

Pt

Idt

1921

4.8

120.9

407.8

1937

8.34

100

551.2

1922

5.42

111.2

460.4

1938

7.78

109.3

511

1923

6.88

100.6

509.2

1939

7.72

104.9

547.9

1924

7.84

90.9

509.3

1940

8.22

97.1

578.8

1925

8.41

81.7

525.6

1941

9.17

120.1

642.7

1926

8.93

92.6

532.3

1942

7.42

119

719.1

1927

8.77

105.6

543.3

1943

5.79

204.7

741.6

1928

9.13

91

545.1

1944

4.45

356.7

798

1929

9.69

95.1

576.2

1945

3.51

449.3

787.2

1930

9.09

85.9

525.2

1946

4.05

338.6

743.2

1931

8.1

102.4

498.2

1947

5.29

263.4

696.4

1932

6.91

107.9

417.4

1948

6.1

236.2

721.2

1933

6.34

95.6

394.3

1949

8.07

159.7

696.7

1934

6.17

107

421.4

1950

10.25

161.8

745.8

1935

6.53

105.2

475.2

1951

11.46

161.2

743.9

1936

7.51

109.3

525.6

1952

11.19

169.4

753.7

a) Divide the data into four equal parts and obtain the regression

Xt=α + β Pt + γ Idt + εt

for each part. Apply Bartlett’s test to check the heteroscedasticity.

b) Repeat part (a) for the regression

ln Xt=α + β ln Pt + γ ln Idt + εt

and again apply Bartlett test and draw conclusion​