Question

In: Statistics and Probability

Consider the model                                     Et = α + β It + ut 

Consider the model

                                    Et = α + β It + ut      where ut has a zero mean

                  Where Et is aggregate expenditure on a good and It is total income. Given the following information

OLS Estimates Using 51 Observations

Dependent Variable Et

Variable

Coeff

STD error

T Stat

constant

0.26644

0.3294

.809

It

0.06754

.0035

19.288

                  SSR = 157.90709

                  Unadjusted R2 = 0.884

                  Adjusted R2 = .881

OLS Estimates Using 51 Observations

Dependent Variable u2t

ut = OLS residuals from earlier regression

Variable

Coeff

STD error

T Stat

constant

-1.3779

2.2407

0.5415

Population

1.3723

.6714

0.465

(Population)2

-0.04724

.03086

.1877

                  SSR = 3684.4776

                  Unadjusted R2 = .119

                  Adjusted R2 = .082

a)   Write down in symbolic terms the auxiliary equation for the error variance implicit in the above information.

b)   State the null hypothesis that there is no heteroscedasticity.

c)   Calculate the value of a test statistic to test this hypothesis.

d)   What is the distribution and degrees of freedom of this statistic?

e)   Carry out the test at a 5% level of significance on whether heteroscedasticity is present or not.

Solutions

Expert Solution

Answer:

Given that,

Consider the model Et = α + β It + ut ,where ut has a zero mean.

Where Et is aggregate expenditure on a good and It is total income. Given the following information.

OLS Estimates Using 51 Observations

Dependent Variable Et.

Variable Coeff STD error T Stat
Constant 0.26644 0.3294 0.809
It 0.06754 0.0035 19.288

SSR = 157.90709

Unadjusted R2 = 0.884

Adjusted R2 = 0.881

OLS Estimates Using 51 Observations

Dependent Variable ut2

ut = OLS residuals from earlier regression

Variable Coeff STD error T Stat
Constant -1.3779 2.2407 0.5415
Population 1.3723 0.6714 0.465
(Population)2 -0.04724 0.03086 0.1877

SSR = 3684.4776

Unadjusted R2 = .119

Adjusted R2 = .082

(a).

The auxiliary equation for the error variance implicit in the above information:

Auxiliary equation for yhe error variance is,

(b).

The null hypothesis that there is no heteroscedasticity:

: Atleast one pair is not zero

[or]

: There is no heteroscedasticity.

:There is heteroscedasticity.

(c).

The value of a test statistic to test this hypothesis:

This is white test for testing heteroscedasticity and test statistic.

Where,

d.f=k*=Number of regression in auxiliary equation.

d.f=2, n=51 observations given.

R2=0.119 (in auxiliary)

T=nR2

=51 0.119

T=5.95

(d).

The distribution and degrees of freedom of this statistic:

(e).

Carry out the test at a 5% level of significance on whether heteroscedasticity is present or not:

Pvalue=0.051047 (From excel formuala CHISQ.DIST.RT(5.95,2))

Clearly Pvalue > 0.05, hence we reject H0 or there is heteroscedasticity present in data.


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