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#2




Lower bound of leverage
Is there any reason why the lower bound of a leveraged point h_ii is 1/n instead of 0?
If we look at the variance of the residual var(e_i) = sigma^2 x (1h_ii); isn't it possible for h_ii = 0 and thus var(e_i) = sigma^2? Thanks
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#3




The proof of the lower bound is mainly matrix algebra that isn't required for the exam. To get some ideas, look at the formula of the leverage for simple linear regression, or equation (3.2.1) in the ACTEX manual. The second term, (x_i  bar(x))^2 / S_xx, is nonnegative, so the leverage is at least 1/n. Equality holds if and only if x_i is exactly equal to the sample mean bar(x).
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Ambrose Lo, PhD, FSA, CERA Associate Professor of Actuarial Science (with tenure) Department of Statistics and Actuarial Science The University of Iowa ACTEX Manual for SOA Exam PA  ACTEX Manual for SOA Exam SRM  ACTEX Manual for CAS Exam MASI Textbook: Derivative Pricing: A ProblemBased Primer (useful for derivatives portion of Exam IFM) 
#6




Any reactions from the September sitting? I'm still spooked out that the SRM threads get no love...
I found that it was, more or less, what I expected. I nailed all fifteenish computational questions that came my way, would estimate that I also nailed 510 of the conceptual, and was able to narrow down the remaining 1015 conceptual questions down to two or three options. Wondering if anyone was surprised (pleasantly or unpleasantly) by the sitting or if, like me, it was kind of like you thought it might be. 
#7




Thanks for checking in. For me work picked up a lot before the exam and unfortunately I couldn't shift things around to get the necessary study time, so I pushed my sitting to January. Good news is that work has lighten up significantly and I plan to have sufficient time to prepare.
I'll be on this thread much more over the next few months and will definitely provide feedback on the exam.
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