Based on a random sample of voters, you run a regression for Y, the approval rating of the current president's handling of the economy (on a 0 to 100 scale). There are several explanatory variables, including the voter's stated party preference (Republican, Democrat, or Independent). Because this is a text variable, you create three dummy variables: R (1 if Republican, 0 otherwise), D (1 if Democrat, 0 otherwise), and I (1 if Independent, 0 otherwise). Which of the following can you conclude? a. If you include all three of these dummies in the regression, the sum of their estimated coefficients will have a meaningful interpretation.
b. If you include only the dummies Randl in the equation, and their coefficients are -5.2 and 1.3, this indicates that all else being equal (i. e., all other explanatory variables remaining constant), Democrats have the lowest average approval rating.
c. If you include only the dummies D and I in the equation, and their coefficients are 3.1 and 1.2, this implies that if you reran the same regression, except with only the dummies Rand I included, the estimated coefficients of R and I would be -3.1 and 4.3.
d. If you include only the dummies D and Rin the equation, and their coefficients are -4.7 and 5.4, this implies that if you reran the same regression, except with only the dummies D and I included, the estimated coefficients of D and I would be 10.1 and -5.4.