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March 18

F-statistic application

In comparing of two models(regressions), using F-statistic, why they should be nested in each other? —Preceding unsigned comment added by 217.219.166.149 (talk) 10:42, 18 March 2009 (UTC)[reply]

If the models aren't nested, then there is no way to build a hypothesis test to carry out with F-values or generic ANOVAs, as far as I know. Hence, your F-statistics serve merely as fitness measures, but nothing more than that (you may dischard one model, but not compare one with another if both seem to adjust well).
On the other hand, if models are nested, possibilities of variance analysis for direct comparisons are straightforward, as with the case of significance of additional variables, etc.
There are some ways of comparing non-nested models: for instance, analysis of information measures, such as AIC, etc. I'd like to mention the article Model selection, as it can be of your interest. Pallida Mors 16:33, 18 March 2009 (UTC)[reply]

AIME

Does anybody know where to find solutions for the 2009 AIME? Lucas Brown 42 (talk) 18:25, 18 March 2009 (UTC)[reply]

http://www.unl.edu/amc/e-exams/e7-aime/archiveaime.shtml should have them at some point. JackSchmidt (talk) 02:59, 19 March 2009 (UTC)[reply]

Prime number problem

You don't need to give me the whole answer, but I need to know how to get started. Find all the prime numbers p with the property that 8p^4-123 is also a prime. Thanks! 76.248.244.232 (talk) 22:43, 18 March 2009 (UTC)[reply]

THIS IS PART OF THE IUPUI MATHEMATICS CONTEST AND THE ORIGINAL POSTER IS TRYING TO CHEAT. 131.215.158.184 (talk) 19:50, 20 March 2009 (UTC) -->[reply]