Drew Christianson
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 Dec 11 revised Running times comparison Corrected formating Dec 11 suggested approved edit on Running times comparison Dec 11 answered Calculating position along the hypotenuse Dec 11 revised How can I find the square root using pen and paper? edited body Dec 11 answered How can I find the square root using pen and paper? Dec 10 answered Probability cut-off Dec 10 comment Probability cut-off I'm curious as to the context of your question. A brief foray into google seems to indicate that 'Event Rate' is associated with biostatistics/Evidence-Based Medicine. So, what context is this in? Dec 7 comment Ranking a set – is pair-based voting a good idea? My voting theory professor was fond of illustrating that, holding the preferences a population of voters constant, one could make successive pairwise votes favor any option by the introduction of specific polarizing options and careful ordering of votes. Thus, I'm inclined to say that the efficacy of ranking by pairs depends somewhat strongly on your set and choice of voting procedure. If you're ranking a large set and pairwise elections are random and repeated, I think it's not an terrible system. Could you expand upon the nature of the problem a bit? Dec 7 comment Simple probability problems @norbert if you really want to stick with the unordered view, you have to use the probabilities at the end of Dilip's comment. There are 3 equally likely unordered pairs that sum to 7: (1,6),(2,7),(3,4) each with a probability of $\frac{2}{36}$. So, we sum the probabilities of those pairs and get a total probability of $\frac{6}{36} = \frac{1}{6}$ Dec 7 comment Simple probability problems @norbert to roll two dice. Consider: rolling a pair of dice and totaling the scores should be completely identical to roll one die twice in succession and taking the total of the two rolls. In the latter case, I think you would agree that rolling a 4, then a 3 is not the same as rolling a 3, then a 4. Precisely the same process is at work in the former case, so we count the sample space in the same way. Dec 7 comment Simple probability problems @norbert You can't just reject the assumptions of the model you're using to calculate the probability and expect it to provide good results. Consider your first problem - the black balls are indistinguishable from each other, but, when calculating the probability of drawing one, it would be incorrect to state that, since one cannot tell them (or their white counterparts apart) then there is only $\binom{2}{1}$ ways to pick one ball. In the same way, while it's clear that (3,4) and (4,3) are effectively the same roll, they are distinct for the purposes of calculating the total number of ways Dec 7 comment Simple probability problems Sorry about that, it checked out in the preview but apparently the full MathJax doesn't like mismatched  and $Dec 7 revised Simple probability problems added 1 characters in body Dec 7 answered Simple probability problems Dec 5 revised indicator variable are uncorrelated, if they are independent? rewrote to put implications in the standard order (if->then). If this isn't ok, sorry, feel free to reject. Dec 5 suggested approved edit on indicator variable are uncorrelated, if they are independent? Dec 5 answered Completing the square Dec 4 comment Completing the square So, the first equation is equal to (A^2 +B^2+C^2) and the second to the multiple of it? And are you allowed matrix algebra to solve systems of linear equations? Dec 4 comment Geometric series Additionally, what is the context of this problem? It looks closest to finding the PV of a growing annunity, but its not exactly the same. Dec 4 comment Geometric series @james$r=\frac{v}{1.05}$in dls's answer is$\frac{1}{1.05^2}\$ as well.