Recent content by WCMU101

Thank you both very much - those answers were excellent! My headache has disappeared. Also, thank you haruspex for replying to my other posts - I should get you to do my phone interview for me haha Thanks again! Nick.

Question is: "If you roll a fair coin 10 times what is the expected product of number of heads and number of tails?" Someone answered 25 at at glassdoor.com. My answer would be: E(k(10-k)) where k is the rv representing the number of heads thrown. = 10E(k) - E(k^2) = 10*mean - (var +...

I'm struggling with Bayes' theory. Please consider the following: Example 1: Submarine sinks if one missile hits it. Two ships aim at submarine and fire one missile each. Ship 1 shoots missile X1, ship 2 shoots missile X2. P(X1 hitting = 0.8) P(X2 hitting = 0.5) P(X1 and X2 hitting | submarine...

That first question was (apparently) asked in an interview - generally no calculators/computers. I didn't think it was possible to integrate the normal pdf analytically. It is easy to work with the normal pdf when you are working in terms of standard deviations (68-95-99.7 rule). Calculating...

Thanks for the quick reply! Regarding the first question: Could you come up with that answer without electronic aid? It approaches the normal distribution due to central limit theorem and the mean is 10000 and variance 20000*.5*.5=5000. So I could write the pdf, but I could not do the...

Doing a bit of study for an interview. Came across this question: "n unbiased coins. What is the probability that half of them exactly are heads. Answer the question for n= 2, 3, 20000." My answers would be: n = 2: p(1h) = 0.5 n = 3: p(1.5h) = 0 n = 20000: p(10000h) = approx. 0 (close...

Hey all. On Wiki (http://en.wikipedia.org/wiki/Fourier_transform#Properties_of_the_Fourier_transform) they have some really good pictures explaining the Fourier transform - see the introduction section. The Fourier transform is of an exponentially decaying sinusoid - where the sinusoid...

Thanks micromass!

Hey all, I'm working on a derivation at the moment and I'm just wondering how I can write this mathematically. I've attached by current attempt (see attachment). What I'm trying to say is: N is an integer and is constrained to an interval of [-a,+a], where a is real. Is my 'syntax'...

Problem: A = n by m matrix x = m by 1 vector y = n by 1 vector C = c by m matrix E = e by m matrix Alpha, gamma and theta are constants. norm(Ax-y) = min subject to: norm(Cx) = alpha norm(Ex) = gamma transpose(Cx)*Ex = (alpha^2)*(gamma^2)*cos(theta) I read a paper on how to do this with 1...

Hey all. I'm not too sharp on linear algebra. I've done a first year university course on it, but that was a couple years ago & didn't go into much detail. Here is the problem: Matrix I (n,1). Matrix N (m,1). Matrix G (n,m). Now... I is a column vector of computed "double differences". These...

Thanks for that! Exactly what I needed to know. Nick.

Hey all. I've written an algorithm to find the Cholesky decomposition of a symmetric, positive-definite matrix (A). I've used the algorithm from: http://en.wikipedia.org/wiki/Cholesky_decomposition#Avoiding_taking_square_roots Ok here is my question. My current algorithm solves for A = LDLT...

Hey all. I'm going through my textbook at the moment and struggling to figure out something. Here is the ideal Brayton cycle (same as in my text). Now I want to find q in, so: The first law of thermodynamics can be written as (neglecting changes in ke and pe): h_in - h_out + q_in - q_out +...