Correlation Definition and 370 Threads

Say I have 2 separate predictor variables x and y. And the response variable is z. The correlation between x and z is a; the correlation between y and z is b. How to get the p-value for a = b? By using SAS or SPSS. I believe we should use t-test. Because the correlation analysis for...

Hi, I read that the dimension of an attractor is not necessarily an integer. I then tried to compute the dimension of the attractor defined by the system I’m studying but I found two definitions for the dimension: -The capacity dimension; -The...

Hi there, I am learning the basics of QFT at the moment. Could someone explain to me, in the case for any number of scalar fields, the difference between correlation functions and scattering amplitudes please? Correlation functions <0|T(\phi_{1}...\phi{n})|0> Does one always write the...

Does anyone know why: <m(k)m(p)>=(2 \pi)^3 \delta(k+p)|m(k)|^2 where m(k) and m(p) are the Fourier transform of the order parameter density and the angled brackets <> stand for an ensemble average? For example, the magnetization M is given by: M=<\int d^3r m(r)>

Why are they useful, what do they denote (physically or otherwise)...

Homework Statement For my homework i have to compute a correlation function in excel from available data. Data goes somewhat like this: 1 xxx yyy 2 xxx yyy 3 xxx yyy I now I have to calculate...

I am searching for correlation with science and atheism/agnosticism. If this thread conflict with the rules (which I don't think it does), I accept that. If so, just remove it. If allowed: Discuss the correlation between science and atheism/agnosticism.

First off, thanks for taking the time to read this. I am not a Physics Major, I am not a scientist. I do try to think a great deal about our existence, and what our future holds as far as discovery, so therefore, I have something to present. It is hypothetical, but please play along with it...

1. Let N and T be the number of users logged on and the time until the next log-off. The joint probability of N and T is given by P(N=η, X≤t) = (1-ρ)ρ^{η-1}(1-e^{-ηλt}) for η=1,2,...;t>0.) Find the correlation and covariance of N and T. 2. COV(X,Y) = E[XY]-E[X]E[Y] ρ_{X,Y} =...

Hi, I can't get my head around this question. Homework Statement The Bell state: |\psi\rangle = \frac{1}{\sqrt{2}}\left(|\uparrow_1\rangle|\downarrow_2\rangle +|\downarrow_1\rangle |\uparrow_2\rangle \right) Find the correlation coefficient of the measurement of the spins in the directions...

matter in The universe is thought to be made up of 75 percent hydrogen and helium is thought to make up 25 percent of helium; Dark matter is thought to make up 25 percent of the universe and 75 percent dark energy; that's an interesting coincidence. , and currently physicists are not certain...

Dear all I have the following problem. Given a set of correlated binary variables, can I determine the joint probability from the correlation function? {Xi} is a set of binary variables Pr(Xi=1) = p and Pr(Xi=0) = q for all i Corr(Xi Xj) = cij cij is symmetric Now how can I determine the...

Correlation between "Snowball Earth" and Cambrian Explosion I know there is a theory that the Earth was once covered in ice that precisely pre-dates the cambrian explosion. is there a leading idea of how snowball Earth allowed for the blossoming of multicellular organisms? Did the ice sheets...

I'm trying to understand the Wiener Filter, and I have a few questions. 1. How can there be such a thing as a correlation matrix of 1 vector. I read here: R_yy = E[ y(k) * y^T(k) ] where y(k) is a vector, and y_T(x) is the same vector transposed. I thought correlation represents the...

(I moved this from the Homework section. I hope it is okay I am posting here.) Homework Statement We are given six cross sections each spaced 2km apart and from these we are supposed measure the slip of the fault, and map the hanging-wall and footwall cutoffs to another worksheet that is...

Homework Statement We are given six cross sections each spaced 2km apart and from these we are supposed measure the slip of the fault, and map the hanging-wall and footwall cutoffs to another worksheet that is the map view of the cross sections. Once we have mapped all of the cutoffs and...

Homework Statement Let Y= X1 + X2 and Y2 = X2 + X3 where X1 X2 and X3 are three independent random variables. Find the joint mgf and the correlation coefficient of Y1 and Y2 provided that a) Xi has a Poisson distribution with mean mi i = 1, 2, 3 b) Xi is N(mi, si2) i = 1, 2, 3 The...

Homework Statement Let X1 and X2 be independent random variables with nonzero variances. Find the correlation coefficient of Y = X1X2 and X1 in terms of the means and variances of X1 and X2. Homework Equations The answer is given as: [ m2s1 ] / [ sqrt( s12s22 + m12s22 + m22s1^2 )] where m =...

is there any corrolation between thermal conductivity coefficient and molecular wieght Mw according to the units [K] W/(m·K) it is independant of mass units (kg or g/mol etc) in my question i am asked to show with a graph, but i have no idea what graph they are talking about

Hi all, The correlation coefficients (Pearson's) is usually defined in terms of discrete sampling of a function. However, I have seen that the mean and standard deviation, for example, are also typically written in terms of discrete variables BUT may also be expressed in terms of a...

Hi everyone, I'm working through Section 9.2 (Functional Quantization of Scalar Fields) from Peskin and Schroeder. I have trouble understanding the absence of a term in equation 9.41 which I get but the authors do not. Define \phi_i \equiv \phi(x_i), J_{x} \equiv J(x), D_{xi} \equiv...

Can someone tell me where algal blooms occur? I'm basically interested in knowing if they're more frequent in certain latitudes (colder regions).

I offer you the solution of a fundamental problem of physics: the relationship between the matter (body) and the field. Many outstanding minds in theoretical physics, including Einstein, tried to resolve this problem, but failed. If 1924 French physicist Louis de Broglie put forward a...

Hi everyone I am trying to get equation 4.29 of Peskin and Schroeder from equation 4.28. This is what I did |\Omega\rangle = \lim_{T\rightarrow\infty(1-i\epsilon)}\left(e^{-iE_{0}(t_{0}-(-T))}\langle\Omega|0\rangle\right)U(t_0, -T)|0\rangle Take the Hermitian Adjoint of both sides. \langle...

Hi, I was going through section 9.2 of Peskin and Schroeder, and came across equation 9.16 which reads \int\mathcal{D}\phi(x) = \int \mathcal{D}\phi_{1}({{\bf{x}}}) = \int \mathcal{D}\phi_{2}({{\bf{x}}}\)int_{\phi(x_{1}^{0},{\bf{x}})\\\phi(x_{1}^{0},{\bf{x}})}\mathcal{D}\phi(x) What does the...

correlation, linear or curvilinear... Hello Forum, usually the Pearson coefficient is meaninful to find the linear relationship between two variables. What if the relationship is not linear? How about quadratic? I heard of the Spearman’s rank correlation coefficient, which does not depend...

Hello people, I don't understand the relation between those concepts, I tried to read what's written in wikipedia about them but no use. Can someone please elaborate more about the relation between them in some intuitive manner? Thank you :)

1 Let X be a normal variable with mean 0 and variance 1. Let Y = ZX where Z and X are independent and Pr(Z = +1) = Pr(Z = -1) =1/2. a Show that Y and Z are independent. b Show that Y is also normal with mean 0 and variance 1. c Show that X and Y are uncorrelated but dependent. d Can you...

Does anyone know if there is any correlation between these two?I mean most of the times during El Nino events the weather here in Europe gets ''crazy'' but till now i haven't seen any formal scientific survey which describes it with certainty. Now with the new El Nino being formed what kind of...

I can generate two random sequences X[i] and Y[i] with no correlation. For example, X[i] = rand(0,1) Y[i] = 100 + rand(0,1) Now, if I plot Y as a function of X, and scale it to a square, I get a random distribution of points showing no correlation (as expected)...

I'm stuck on this problem: Let X be uniform[0,1] and Y be uniform[0,X]. Calculate the covariance and correlation between X and Y. thanks

Hello, First time post long time lurker! I've got an interesting project I am working on which involves a few MechE subjects. The overall goal (for now) is to determine the drag force of a cylindrical cone headed object in sand under various pressures. The movement of the cylinder is the tricky...

Homework Statement Let X be a random vairable which can only take three values: -1,0,1 and they each have the same probability. Let Y also be a random vairable defined by Y = X2. Show that i) X and Y are not independent ii) X and Y are uncorrelated Homework Equations To show that two...

Homework Statement Let Q^(1) be the position of some object that we wish to measure, and let Q^(2) and P^(2) be the position and momentum of the indicator variable of a measurement apparatus. Show that an interaction of the form H_int = cQ^(1)P^(2)(dirac delta(t)) will induce a correlation...

I would appreciate some help with this problem. Assuming X and Y are independent, I'm trying to find the correlation between XY and Y in terms of the means and standard deviations of X and Y. I'm not sure how to simplify cov(XY,Y)=E(XYY)-E(XY)E(Y) =E(XY^2)-E(X)E(Y)^2. If X and Y are...

I would appreciate some help with this problem. Assuming X and Y are independent, I'm trying to find the correlation between XY and Y in terms of the means and standard deviations of X and Y. I'm not sure how to simplify cov(XY,Y)=E(XYY)-E(XY)E(Y) =E(XY^2)-E(X)E(Y)^2. If X and Y are...

What are the general properties of 3-point correlation function of a spin-2 field? And what about 4-point, 5-point correlation functions? spin-3, spin-4 fields? What mathematical category do these problems belong to? Are there any specific studies on them? (They are so widely used in...

I had a question on a test this past friday that left me absolutely scratching my head. "The greater the density of a liquid the greater its ...?" 1 volume 2 area 3 viscosity 4 buoyancy While viscosity seems like the best option, this question was for a piping/plumbing test, and...

the correlation between A and B is 0.8 and between B and C is 0.9. I have to calculate what the least correlation A and C can be. \begin{pmatrix} 1 & 0.8 & x\\ 0.8 & 1 & 0.9\\ x & 0.9 & 1 \end{pmatrix} using sthe standard equation for eigenvalues you get...

When dealing with system containing millions of particles( for example, charged particles or magnetic particles) with statistical mechanics, I may often see the description or explanation that the certain effect is due to the coupling or correlation of particles. So can anybody give me a...

Hello All, I just read in a book that springs are pretty much analogous to capacitors in terms of energy considerations to capacitors. For eg. If a mass m suspended by a spring comes to rest after downward displacement y, Assuming compression = y for equilibrium, mg=ky thus k = mg/y...

How to do correlation using a set of data?

Is it generally true that the ground state of a given quantum system corresponds to the lowest quantum numbers? If so, how do we know this?

Homework Statement I have have a set of data pairs (x, y); (1, a) (2, b) (3, c) (4, d) (5, e) (6, f) (7, g) The least squares regression line for the this set is y=3x-12 Determine the new gradient of this line if the original set of scores has been transformed to; (6, a+3)...

I wasn't sure where precisely to put this, hopefully it gets an answer here. In my computational physics class we just learned about the correlation dimension. I know how to compute it, but don't quite know what it means. I learned roughly that the correlation dimension of something is a...

I am going through some of the problems in a statistical physics book. I am stuck on the following question: If we have two random variables X and Y, related by Y=mX + b => y(i) = mx(i) + b, where b and m are deterministic, prove that corr(X,Y) = m/sqrt(m^2) = sgn(m), where sgn(m) is the...

[SOLVED] Help with variance sum + correlation coefficient formula This is a worked example The objective is to prove -1 \leq \rho(X,Y) \leq 1 Then the book uses this formula... (2) 0 \leq Var(\left \frac{X}{\sigma_x} + \frac{Y}{\sigma_y} \right) (3) = \frac{Var(X)}{{\sigma_x}^2} +...

1. A system of 7 objects each have one measurement taken of them. These measurements are to be compared with two theoretical models, which theoretical model does the data fit best?[br]The machine used to measure the values has an extremely small error, so the data gathered does not have...

Homework Statement A signal x(t) is transmitted and received back as y(t) and sampled in the receiver, so we get a DT signal y[n] = ax[n-D] + w[n], where w[n] is noise baiscally i need to explain how we can measure the time delay by computing crosscorrelation Ryx(l). My undestanding is...

Homework Statement This is a question from an exam in fractals and chaos. The paper is attached, the question is the first one, part (b). Homework Equations In the paper The Attempt at a Solution Am I expected to compute continuous correlation functions with respect to epsilon...