Recent content by johnaphun

Hi chiro, thanks for the reply. No I'm unaware of these theorems, would be able to explain for me?

Sorry that's meant to be phi not an empty set. I typed this without my glasses! It's meant to represent the dispersion/scale parameter For the poisson distribution I did the following; f(y;θ) = λye-λ/y! = exp{log(λy/y!)} = exp{ylogλ - λ - logy!} with θ =...

I've been asked to prove that the following distribution is a member of the generalised exponential family of distributions. f(y;β) = (ky2β(y+k))/((β+3)(y+2k)(y+1)1/2) I know that i have to transform the equation into the form f(y) = exp{(yθ-bθ)/a∅ +c(y,∅)} and that to do this i...

Hi thanks for the reply, I've not been given any pdf function, I've only been told that Xi is standardised normally distributed and to thus find the MGF for Xi (which i can do) and (Xi)2. I assume it's asking for me to find an MGF for a random variable Xi with chi distribution which is (1 −...

Hi guys, I need to find the moment generating function for X ~ N (0,1) and then also the MGF for X2 . I know how to do the first part but I'm unsure for X2. do i use the identity that if Y = aX then MY(t) = E(eY(t)) = E(e(t)aX) or do i just square 2pi-1/2e x2/2 and then solve as...

Homework Statement A risky portfolio P is to be formed from securities S1 and S2 where the expected returns are E(R1) = 0:05 and E(R2) = 0:1, the variances are s122 = 1 and s22 = 2 and S1 and S2 are uncorrelated. Suppose no short selling is allowed so that P= x1S1 + x2S2, x1 + x2 = 1...

Homework Statement The model for the resistivity of metals can be described differently by adding the scattering term into the electron equation of motion. mx'' + (2m/t)x' = qE Where x is a mean quantity. DC conductivity is found by considering the steady state when E is constant. Show...

Don't worry guys, I've figured it out!

Homework Statement Find all vE(Z2)5 for which d(v;11011) = 3 Homework Equations I'm sure this one isn't too difficult, I'm just unsure how to go about attempting it

Homework Statement Convert the differential equation for x, x''' + 2(x''2) = 0 Into a system of first order differential equations. Put the system in vector form Homework Equations The Attempt at a Solution I'm able to do this for simpler DE's but I can't seem to find an...

Thanks for the quick response and apologies for my slow one! Don't worry i manage to solve it in the end, silly miscalculations on my part. Thank you for the help anyway!

Homework Statement Write down an expression for ∇^2 in Cartesian co-ordinates and, by expressing the displacement vector r in Cartesians show that: ∇^2 ⎛ 1/r ⎞ = 0 for r > 0. Homework Equations I can do the first part of the question and i know how to show that ∇^2 ⎛ 1/r ⎞ = 0 in...