答案和详解如下： Q6. Carter realizes that although regression analysis is a useful tool when analyzing investments, there are limitations. Carter made a list of points describing limitations that Smith Brothers equity traders should be aware of when applying her research to their investment decisions. - Point 1: Data derived from regression analysis may be homoskedastic.
- Point 2: Data from regression relationships tends to exhibit parameter instability.
- Point 3: Results of regression analysis may exhibit autocorrelation.
- Point 4: The variance of the error term changes over time.
When reviewing Carter’s list, one of the Smith Brothers’ equity traders points out that not all of the points describe regression analysis limitations. Which of Carter’s points most accurately describes the limitations to regression analysis? A) Points 2, 3, and 4. B) Points 1, 2, and 3. C) Points 1, 3, and 4. Correct answer is A) One of the basis assumptions of regression analysis is that the variance of the error terms is constant, or homoskedastic. Any violation of this assumption is called heteroskedasticity. Therefore, Point 1 is incorrect, but Point 4 is correct. Points 2 and 3 also describe limitations of regression analysis. Q7. Which of the following is least likely an assumption of linear regression? The: A) expected value of the residuals is zero. B) residuals are independently distributed. C) residuals are mean reverting; that is, they tend towards zero over time. Correct answer is C) The assumptions regarding the residuals are that the residuals have a constant variance, have a mean of zero, and are independently distributed. Q8. Which of the following is least likely an assumption of linear regression? A) The residuals are normally distributed. B) The variance of the residuals is constant. C) The independent variable is correlated with the residuals. Correct answer is C) The assumption is that the independent variable is uncorrelated with the residuals. Q9. The assumptions underlying linear regression include all of the following EXCEPT the: A) disturbance term is normally distributed with an expected value of 0. B) independent variable is linearly related to the residuals (or disturbance term). C) disturbance term is homoskedastic and is independently distributed. Correct answer is B) The independent variable is uncorrelated with the residuals (or disturbance term). The other statements are true. The disturbance term is homoskedastic because it has a constant variance. It is independently distributed because the residual for one observation is not correlated with that of another observation. Note: The opposite of homoskedastic is heteroskedastic. For the examination, memorize the assumptions underlying linear regression! Q10. Linear regression is based on a number of assumptions. Which of the following is least likely an assumption of linear regression? A) There is at least some correlation between the error terms from one observation to the next. B) Values of the independent variable are not correlated with the error term. C) The variance of the error terms each period remains the same. Correct answer is A) When correlation exists, autocorrelation is present. As a result, residual terms are not normally distributed. This is inconsistent with linear regression. | 
发表于 2009-1-5 10:10
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