
Answer-first summary for fast verification
Answer: I and IV only
## Explanation Let's analyze each statement: **Statement I**: "In the ordinary least squares (OLS) model, the random error term is assumed to have zero mean and constant variance." - **CORRECT** - This is one of the key assumptions of OLS regression: E(ε) = 0 (zero mean) and Var(ε) = σ² (constant variance/homoscedasticity) **Statement II**: "In the OLS model, the variance of the independent variable is assumed to be positively correlated with the variance of the error term." - **INCORRECT** - This is not an assumption of OLS. In fact, if the variance of the error term depends on the independent variable, it violates the homoscedasticity assumption. **Statement III**: "In the OLS model, it is assumed that the correlation between the dependent variable and the random error term is zero." - **INCORRECT** - The correct assumption is that the independent variable(s) are uncorrelated with the error term, not the dependent variable. The dependent variable is by definition correlated with the error term. **Statement IV**: "In the OLS model, the variance of the residuals is assumed to be constant." - **CORRECT** - This is the homoscedasticity assumption, which means the variance of the error term (and therefore the residuals) is constant across all observations. Therefore, only statements I and IV are correct, making option C the correct answer.
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Which of the following statements about the ordinary least squares regression model (or simple regression model) with one independent variable are correct?
I. In the ordinary least squares (OLS) model, the random error term is assumed to have zero mean and constant variance.
II. In the OLS model, the variance of the independent variable is assumed to be positively correlated with the variance of the error term.
III. In the OLS model, it is assumed that the correlation between the dependent variable and the random error term is zero.
IV. In the OLS model, the variance of the residuals is assumed to be constant.
A
I, II, III and IV
B
II and IV only
C
I and IV only
D
I, II, and III only
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