A survey of earnings contains an unusually high fraction of individuals who state their weekly earnings in 100s, such as 300, 400, 500, etc. This is an example of
A. errors-in-variables bias.
B. sample selection bias.
C. simultaneous causality bias.
D. companies that typically bargain with workers in 100s of dollars.
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In the case of errors-in-variables bias,
A. maximum likelihood estimation must be used.
B. the OLS estimator is consistent if the variance in the unobservable variable is relatively large compared to variance in the measurement error.
C. the OLS estimator is consistent, but no longer unbiased in small samples.
D. binary variables should not be used as independent variables.
Sample selection bias occurs when
A. the choice between two samples is made by the researcher.
B. data are collected from a population by simple random sampling.
C. samples are chosen to be small rather than large.
D. the availability of the data is influenced by a selection process that is related to the value of the dependent variable.
Simultaneous causality
A. means you must run a second regression of X on Y.
B. leads to correlation between the regressor and the error term.
C. means that a third variable affects both Y and X.
D. cannot be established since regression analysis only detects correlation between variables.
Correlation of the regression error across observations
A. results in incorrect OLS standard errors.
B. makes the OLS estimator inconsistent, but not unbiased.
C. results in correct OLS standard errors if heteroskedasticity-robust standard errors are used.
D. is not a problem in cross-sections since the data can always be "reshuffled."
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