>Hi, > >I am working on a section in my text book on unbiased estimators, and for >several of the problems I have to find the expected value of x squared. I >have the solutions manual for the text book, but I can't figure out how they >computed the expected value. For example, for a binomial distribution with >parameters n, p and q = 1-p, they have the expected value of x squared >equals npq+n^2*p^2. Can someone please explain how they get this? Another >example is for a poisson distribution with parameter L. They have the >expected value of x^2 as L + L^2. Do I have to use the formula for the >expected value of x^2 and compute the sum? This seems very difficult for >both of these distributions. > >Thanks, >Kevin
The answer is yes. There are tricks to obtain E(X^2), such as deriving E(X(X-1)) = E(X^2) - E(X) then adding back E(X) but it's definitely worth your time to work out these problems at least once on your own. . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
