Variables Definition and 1000 Threads

Hi I have a certain experiment that I repeat 40 times and get the result: 0.001 +/- 0.004. Now I've repeated the experiment using a different method (so it is essentially a new experiment) and I get a new value: -0.002 +/- 0.003 Now, is it true to say there is no statistically...

Greetings- In trying to solve a thermal stress problem, I have encountered an inhomogeneous differential equation of the following general form: \nabla^2 \Phi(r,z) = F_r(r)F_z(z) Solving the homogeneous case is no problem, as it is kind of a classic. Is there a route to finding a particular...

Dyadic Cube C_{k,N} = X \in\ \mathbb{R}^{n} \frac{k_{i}}{2^{N}} \leq x_{i} < \frac{k_{i}+1}{2^{N}} for 1 \leq i \leq n Where k = \pmatrix { k_{1} \cr k_{2} \cr \vdots \cr k_{i} \cr } I understand that N is the level of the cubes, but what does k equal? I'm having trouble...

Homework Statement Let S be the part of the cylinder of radius 9 centered about z-axis and bounded by y >= 0; z = -17; z = 17. Evaluate \iint xy^2z^2 Homework Equations The Attempt at a Solution So I use the equation x^2 + y^2 \leq 9, meaning that r goes from 0 to 3 Since y...

Evaluate the limit or prove that it does not exist.. f(x,y) -> (0,0) 3xy/((x^2)+(4y^2)) The attempt at a solution: Set x to 0 and you get 0 set y to 0 and you get 0 set y=x and you get 3x^2/5x^2 = 3/5 This means that limit does not exist. Is this correct? If this is correct, how...

we have X,Y variables and their common density f(m,n)=P(X=m,Y=n) where f(0,1)=0.1 f(1,0)=0.1 and f(1,1)=0,31 find P(X=0) i think that P(X=0)= f(0,1) but it says that its incorrect what i am doing wrong?

I have a question regarding the paper by John Bell (www.drchinese.com/David/Bell_Compact.pdf‎ ) in which he shows that a certain hidden variable approach cannot reproduce the expectation values predicted by QM for a pair of particles in the singlet state. After eqn 15 on page 4, I don't...

Hello. I have a problem with probability theory task. The task is: X and Y is independent random variables with same density function fx=fy=f. What will be probability of P(X>Y). This P(X>Y) reminds me a cdf: P(X>Y)=1-P(X<Y)=1-cdf of X. Cdf of x is equal to integral ∫f dx from -inf to...

Let x(1),...,x(N) all be independent uniformally distributed variables defined on (0,1), i.e. (x(1),...,x(N)) - U(0,1). Define the random variable y(i) = x(i)/(x(1)+...+x(N)) for all i=1,...,N. I’m looking for the pdf of the random variables y(1),…,y(N). Has anyone come across such random...

Give a parametric equation for a curve in 2 dmiensions (x(t),y(t)) it may sometimes be possible to rotate or otherwise transform coordinates so that the tranformed curve becomes a function y = f(x) (as opposed to merely a relation such as x^2 = y^2 + 1). More generally, if we have a curve...

http://sphotos-h.ak.fbcdn.net/hphotos-ak-ash4/485580_10200547582988715_854455727_n.jpg In formula 1 it says F(1) = F(0)+F'(0)+ 0.5F''(C) Where the heck dos the C come from? I thought they were applying taylor's formula to find an approximation of F(1), around t=0. Then c=0, right? Is it...

From the two equations given below, find ∂s/∂V (holding h constant) and ∂h/∂V (holding r constant V = π*r^2*h, S = 2π*r*h + 2*π*r^2 Not entirely sure where to start...

Homework Statement We have two independent, exponentially distributed random variables X and Y (with parameter a). Z = X/(X+Y) What is Z:s distributon function? Homework Equations The Attempt at a Solution I think I need some intuition to what I'm really doing with these, I'm having a...

1. Homework Statement [/b] this problem is on page 267 of Advanced calculus of several variables by Edwards, I just can't seem to get a handle on it: Let aA be a contented set in the right half of the xz plane ,x>0. Define $$\hat{x}$$, the x-coordinates of the centroid of A, by...

Homework Statement Find correlation between random variables x and y in the following: $$P_{x,y}(x,y)=A \ xy \ e^{-(x^2)}e^{-\frac{y^2}{2}}u(x)u(y)$$ Homework Equations The co-variance ##\sigma_{xy}=\overline{(x-\bar{x})(y-\bar{y})}## or ##\sigma_{xy}=\overline{xy}-\bar{x}\bar{y}##...

I didn't post this in the probability section cause the questions I have are more regarded to communication system engineering. I haven't actually been able to wrap my head around these concepts mainly cause all the study material I use have these really ambiguous explanations of each...

Hi, I would certainly appreciate it if you could please confirm the result I obtained to the following Statistics problem. Homework Statement A tank is supplied with fuel once a week. If the fuel (in thousands of liters) that the station sells in a week is a random variable which is...

Homework Statement The question is: Let \phi: \mathbb{R}^n\rightarrow\mathbb{R}^n be a C^1 map and let y=\phi(x) be the change of variables. Show that dy_1\wedge...\wedge dy_n=(detD\phi(x))\cdotdx_1\wedge...\wedgedx_n. Homework Equations n/a The Attempt at a Solution Take a look at here and...

The question is: Let $\phi：\mathbb{R}^n\rightarrow\mathbb{R}^n$ be a $C^1$ map and let $y=\phi(x)$ be the change of variables. Show that d$y_1\wedge...\wedge $d$y_n$=(detD$\phi(x)$)$\cdot$d$x_1\wedge...\wedge$d$x_n$.Take a look at here and the answer given by Michael Albanese: differential...

Hi everyone, I have the following exercise. Fx(x)=0, x<-1 or x>1 Fx(x)=1/2, x=[-1;1] g(x)=x^2+1 --- this is the function of random variable I must calculate Fy which is the sum of solutions of g(xk)=y , Fy(y)=sumFx(xk)/|g`(xk)| g(x) is bijective on [-1;1] y=x^2+1=> x=+sqrt(y-1) or x=-sqrt(y-1)...

Hi, I'm trying to find a probability distribution (D) with the following property: Given two independent stochastic variables X1 and X2 from the distribution D, I want the difference Y=X1-X2 to have a uniform distribution (one the interval [0,1], say). I don't seem to be able to solve it...

For some time now I've been trying to figure out probably for a problem of the following form. Say a criminal profiler is trying to determine the probability that someone is a criminal based on statistical information. 60% of people who have mustaches are criminals. 70% of people who...

Hi Everyone! I have two normally distributed random variables. One on the x axis, the other on the y axis, like a complex normal random variable. I'm trying to find the pdf of the angle between a fixed point on the x-y plane(let's say point 1,0) and the vector formed by combining the two...

I've found many articles online that explain how to solve the Schrodinger equation for a potential dependent on x, but not for one dependent on t. A couple articles said that you could not use separation of variables to solve the Schrodinger equation with a time dependent potential, but they did...

Suppose I have a Schrodinger equation for two interacting particles located at x and y; so, something like \left( i \frac{\partial}{\partial t} + \frac{1}{2m_x} \frac{\partial^2}{\partial x^2} + \frac{1}{2m_y} \frac{\partial^2}{\partial y^2} + V(x-y) \right) \psi(x,y,t) = 0. Now, I want to...

Oke this is a simple question but it has me a bit stumped. Given a random variable X with a uniform probability distribution between [0,2]. What is the probability distribution function (pdf) of X^2 ?

Hi everyone, I would like to know if this stament is true or not. I have two variables u,v both of them distributed as normal distribution with mean 0 and variance a^2. Is it true that the expected value of uv is a^2 ? Thanks

Homework Statement Let X and Y have the joint probability density function f(x,y)=k(1-y), if 0<x<y<1 and 0 elsewhere. a)Find the value of k that makes this pdf valid. b) Find P(X<3/4,Y>1/2) c) Find the marginal density function of X and Y d) Find the expected value and variance of X and...

Ok - this is a moderately tough question which I can't figure out. So I am trying to work on a simplified model to start with. I imagine a solid, very massive impenetrable object. I have a tube or any long object which can exhibit some elastic behavior and also plastic behavior...

Homework Statement The joint PDF (probability density function) ##p_{X,Y}(x,y)## of two continuous random variables by: $$ p_{X,Y}= Axy e^{-(x^2)}e^{\frac{-y^2}{2}}u(x)u(y)$$ a) find A b) Find ##p_X (x), \ p_{y}, \ p_{X|Y}(x|y), and \ p_{Y|X}(y|x)## Homework Equations The first...

Hi, I don't quite understand when finding eigenvectors there is usually a free choice of variables to pick, and you can sub in any number to find an eigenvector. Could anyone please explain how this works (and why you can sub in any number), as this usually comes up in vector problems with 3...

Homework Statement Consider the ideal Stirling cycle working between a maximum temperature Th and min temp Tc, and a minimum volume V1 and a maximum volume V2. Suppose that the working gas of the cycle is 0.1 mol of an ideal gas with cv = 5R/2. A) what are the heat flows to the cycle during...

Hi there, I have a table with two variables that relates to a 2d dose distribution and need to determine a formula that will solve for any point on that surface. Similar to determining the equation of a straight line with a few points (y = mx +c) to then be able to calculate any point on the...

Hey everyone, I need to do the following integral. I just need a little help getting this started, I'm not sure where I need to go. Here is the problem: \int_{0}^{1-v} du \int_{0}^{\frac{1}{2}} dv \frac{1}{1+u^2-v^2} I think I have the boundaries for the integral set up correctly, {0≤v≤1/2...

So, as the title may have given away, I'm trying to figure out implicit differentiation in the multiple variable context. I thought a good practice would be the law of cosines, aka c^2 = a^2 + b^2 - 2abcosθ. So I'm trying to find ∂θ/∂a, ∂θ/db, ∂θ/dc. I tried solving for θ and then taking...

Why is the "Separation of Variables" method valid? Hey guys, Lately I have been focusing on some question that have annoyed me for some time. One of these questions is: Why is the method of separation of variables valid when solving some PDE? Usually smmetry arguments are presented, and...

Here is the question: Here is a link to the question: Find the range and domain of function of 2 varibles:? - Yahoo! Answers I have posted a link there to this topic so the OP can find my response.

Homework Statement See figure attached Homework Equations The Attempt at a Solution I am not concerned with part (a), I have deduced that indeed X and Y are dependent. I'm not sure if I have done part (b) correctly, and I am quite certain I have done part (c) incorrectly, but...

Homework Statement Find the absolute extrema of the function on the set D. f(x,y)= x^2 + 4y^2 + 3x -1 D= {(x,y) l x^2 + y^2 ≤ 4} Homework Equations The Attempt at a Solution The only thing I've done so far was find the critical point. I found f-sub x = 2x+3 and f-suby= 8y...

Homework Statement Prove using the formal definition of a limit that \lim_{(x,y) \to (1,2)} 5x^3-x^2y^2 is equal to 1. Homework Equations \lim_{(x,y) \to (1,2)} 5x^3-x^2y^2\\ \left \| \overline{x}-\overline{a} \right \|< \delta \\ \left | f(\overline{x})-L \right |<\epsilon The...

Help -- Seperation of variables problem, multiple solutions. Homework Statement Suppose that dy/dx = √y and y(0) = 0. What is y(x)? There is more than one answer to this problem. You must list five correct solutions. Homework Equations Seperation of Variables/ integration The...

Homework Statement Find values for x, and y in the following statement: [SIZE="2"]2x-y+\sqrt{4x-y}=x-2y+3+\sqrt{x+5} The Attempt at a Solution I've managed to rearrange the equation, but I cannot eliminate or equate the square roots on the LHS: [SIZE="2"]\sqrt{4x-y}-\sqrt{x+5}=-x-y+3

Hello, I have a question about solving or isolating for variables in an equation. It doesn't need to be an equation, however, I've noticed my problems always appear when trying to transpose them. I have read through algebra concepts, but they only tell me what I already know regarding...

Homework Statement I'm trying to take the derivative of the following integral \frac{d}{d V} \int_0^t{V(\tau)}d\tau Homework Equations FTC will probably be a part of it. The Attempt at a Solution I always get confused when I'm taking the derivative of an integral. I know the answer is...

Hello, I'm hoping I might be able to get some help in creating a forecasting model (in sports) looking at 2 variables that are not independent of each other. I'll take US Football (same applies to rugby) as an example. The specific forecast I'm interested in here is the expected supremacy...

Hello there, I am facing the second order ODE in the unknown function $$y(t)$$ $$ \ddot{y} = a \dot{y} y - b \dot{l} l - c\dot{l} + d$$ $$a, b, c, d$$ positive constants, such that $$ \frac{a}{b} = \frac{d}{c}$$ I would like to understand more about it before relying on numerical methods...

I had two of these problems assigned. I have to show that the limit doesn't exist for two separate functions as (x,y) approaches (0,0). The first function was $$\frac{x^4-y^2}{x^4+y^2}$$ and I went about showing the limit didn't exist by approaching along the x-axis to (0,0) and along the y-axis...

I have looked up a few derivations of Noether's Theorem and it seems that chain rule is applied (to get a total derivative w.r.t. q_{s} ( = q + s ) is often used. What I do not understand is why this is legitimate ? If we start with L=L(q,q^{.},t) how can we change to L=L(q_{s}...

I have an extcalc program on my computer. I can't seem to figure out how to get it to plug in "y" variables. (eg. x^2 + y^2) Your widget did this without any problem. (Looked great.) I am just getting underway with trying to understand -- in an elementary way -- certain areas of math based...

Homework Statement I'm trying to solve a system of two second order linear differential equations with the ode45 function. It is a two degree of freedom problem with 2nd order derivatives of both variables, u and theta. I believe that's referred to as a "stiff matrix"). I'm very...