a. Sample selection bias:
a. Is only important for finite sample results
b. Occurs when a selection process influences the availability
of data and that process is related to the dependent variable
c. Results in the OLS estimator being biased, although it is
still consistent
d. Is more important for non-linear least squares estimation
than for OLS
2. Which of the following problems will not cause the
endogeneity problem in a linear regression model?
a. Omitting relevant variables
b. Including irrelevant variables
c. Errors in variables
d. Simultaneous equations
3. The following is not a threat to external validity
a. The treatment being studied is not representative of the
treatment that would be implemented more broadly
b. Experimental participants are volunteers
c. The experimental sample is not representative of the
population of interest
d. Partial compliance with the treatment protocol
4. The conditions for valid instruments do not include the
following:
a. Perfect multicollinearity between the predicted endogenous
variables and the exogenous variables must be ruled out
b. Each one of the instrumental variables must be normally
distributed
c. Each instrument must be uncorrelated with the error term
d. At least one of the instruments must enter the population
regression of X and the Z's and the W's.
5. A study based on the OLS regressions is internally valid
if:
a. The errors are homoscedastic, and there are no more than two
binary variables present among the regressors
b. You use a two-sided alternative hypothesis and standard
errors are calculated using the heteroskedasticity robust
formula
c. Weighted least squares produces similar results and the
t-statistics is normally distributed in large samples
d. The OLS estimator is unbiased and consistent and the standard
errors are computed in a way that makes the confidence intervals
have the desired confidence level
6. The following will not cause a correlation between X and u in
the simple regression model:
a. Irrelevance of the regressor
b. Simultaneous causality
c. Omitted variables
d. Errors in variables
7. The distinction between endogenous and exogenous variables
is
a. Dependent on the distribution of the variables, i.e., when
they are normally distributed, they are exogenous, otherwise, they
are endogenous.
b. Whether or not the variables are correlated with the error
term
c. That exogenous variables are determined inside the model and
endogenous variables are determined outside of the model
d. Dependent on the sample size, i.e., for n sufficiently large,
endogenous variables become exogenous
8. The reliability of a study using a multiple regression
analysis depends on all of the following with the exception of:
a. Omitted variable bias
b. External validity
c. Presence of homoskedasticity in the error term
d. Errors in variables