We are given the following and asked how much of RBC stock’s excess return variation can be attributed to company specific risk.
Regression Statistics Multiple R = 0.7131 R-squared = 0.5086 Standard error of estimate = 0.0269 Observations= 60
This is the solution:
The R2 in this regression is 0.5086. This result suggests that about 51 percent of the total variation in the excess return to RBC stock (the return to RBC above the risk-free rate) can be explained by excess return to the market portfolio. The remaining 49 percent of RBC stock’s excess return variation is the nonsystematic component, which can be attributed to company-specific risk.
Why not use the Standard Error of Estimate to find the SSE which is related to the errors of the regression?
It is idiosyncratic risk. However, the reason isn’t that our goal is to minimize it.
Which is correct.
Evidently the question was intended to mean “What percentage of the total variance is idiosyncratic?” That isn’t clear from what you wrote. You calculated the SSE, but not the percentage of TSS that SSE represents.
The question is not well worded: it would be reasonable to interpret it either as how much absolute variation, or as what percentage of the total variation. On the real exam I would expect there to be no such ambiguity.
Nevertheless, when they give you three answer choices that are all percentages, you can be sure that they meant the latter interpretation, not the former.