Given


Derive the variance of these OLS estimators
(both
)



(a) What is meant by heteroscedasticity? What are the effects of heteroscedasticity on: (i) The OLS estimators? In particular, does heteroscedasticity create bias in the OLS estimators? (ii) The variances and standard errors of the OLS estimators. (iii) The validity of t-test and F-test of overall significance of the regression? (b) Given: Yi = β1 + β2 Xi + ui Var(ui) = σ2 Xi Show how this model can be transformed so that the disturbances have constant variance. Explain how...
What is multicollinearity and how does it affect the standard errors of OLS estimators? (b) In the context of perfect multicollinearity between explanatory variables, explain why the OLS estimators cannot be derived. (c) With what methods can one detect multicollinearity? (d) Given relatively high variance of individual explanatory variables, explain why relatively low t-statistics but a relatively high F-statistic for the regression is an indication of multicollinearity.
Answer each question by writing TRUE or FALSE 1. For OLS estimators to be linear the explanatory variables must be variable, non- stochastic and fixed in repeated samples. Under the conditions of perfect multicollinearity, the OLS estimators are not unique. The presence of heteroskedasticity causes the OLS method to overestimate the variances 2. 3. of the parameters. The Breusch-Godfrey LM test is applicable when a lagged dependent variable is used. If we include a non-influential variable in an equation the...
1. If OLS estimators satisfy asymptotic normality, it implies that a. they are approximately normally distributed in large enough sample sizes b. they are approximately normally distributed in samples with less than 10 observations c. they have a constant mean equal to zero and variance equal to a d. they have a constant mean equal to one and variance equal to a
1. If OLS estimators satisfy asymptotic normality, it implies that a. they are approximately normally distributed in large enough sample sizes b. they are approximately normally distributed in samples with less than 10 observations c. they have a constant mean equal to zero and variance equal to a d. they have a constant mean equal to one and variance equal to a
1. If OLS estimators satisfy asymptotic normality, it implies that a they are approximately normally distributed in large enough sample sizes b. they are approximately normally distributed in samples with less than 10 observations c. they have a constant mean equal to zero and variance equal to a d. they have a constant mean equal to one and variance equal to o
1. If OLS estimators satisfy asymptotic normality, it implies that a they are approximately normally distributed in large enough sample sizes b. they are approximately normally distributed in samples with less than 10 observations c. they have a constant mean equal to zero and variance equal to a d. they have a constant mean equal to one and variance equal to o
1. If OLS estimators satisfy asymptotic normality, it implies that a they are approximately normally distributed in large enough sample sizes b. they are approximately normally distributed in samples with less than 10 observations c. they have a constant mean equal to zero and variance equal to a d. they have a constant mean equal to one and variance equal to o
1. If OLS estimators satisfy asymptotic normality, it implies that a they are approximately normally distributed in large enough sample sizes b. they are approximately normally distributed in samples with less than 10 observations c. they have a constant mean equal to zero and variance equal to a d. they have a constant mean equal to one and variance equal to o
[3] TRUE or FALSE: In the presence of autocorrelation, the OLS estimators remain unbiased but are no longer efficient. [4] TRUE or FALSE: In the presence of autocorrelation, the estimated OLS variances will be unbiased estimators of the correct OLS variances. [5] TRUE or FALSE: The core time series models are the regression or static model, the autoregressive model, the distributed lag model, and the autoregressive distributed lag model.