Read about correlation | 31 Discussions | Page 1

  1. entropy1

    I Ontology of measurement and correlation

    If a non-commuting measurement is made on a quantum property (like spin), this can be seen as the wavefunction being prepared. So you can't tell if the outcome represents the property, or that the property is prepared. However, if the property is prepared, we can predict the correlation with a...
  2. entropy1

    I (In)dependence in entanglement experiments

    If an entanglement experiment, whereby an entangled pair of particles is measured at both ends, is independent of the next entanglement experiment with another pair of entangled particles, how can there be a correlation? It seems that each independent run does not influence the next run, but...
  3. haruspex

    I Justifying a correlation

    all the references I can find on the net to justifying a correlation treat it as a matter of judgment, and, quite correctly, that it depends on the application. But it seems to me that one could compare the fit to the data of a horizontal line (i.e. average y) with that of the linear regression...
  4. entropy1

    B Can this be called 'a coincidence'?

    Suppose we have two variables A and B. A has a truly random distribution over {0,1} with P(0)=P(1)=0.5 . B has the same distribution. Now suppose that A and B always show both a 1 or both a 0. This would be a strong correlation between A and B. Now could this be called 'a coincidence'? And if...
  5. F

    Homework - A galaxy in the local universe

    Homework Statement I have the following questions as homeworks and I would like to get help. Here's some informations given to help us to answer : Photometry : U=11.60 B=11.16 V=10.20 Redshift : z= 0.00780 Central velocity dispersion : ##\sigma_{v}## = 210 km/s Introduction : The...
  6. F

    Homework - Interparticle distance between galaxies

    Homework Statement [/B] I have the following questions as homeworks and I would like to get help. Question 1) Give the formal expression of the total number density of galaxies. Why is this expressoin problematic in practice? Question 2) In practice one uses a numerical value for the number...
  7. entropy1

    I Is a measurement a correlation?

    If we make a measurement, does that mean that the outcome of the measurement gets correlated with the measured value?
  8. entropy1

    I Correlation setup between past and present

    Suppose A is an ensemble of measurement events in the past. Suppose B is an ensemble of measurement events in the present. Suppose there is a correlation between A and B that stays the same over time. Suppose we can manipulate the outcomes of B (for example by choosing the orientation of the...
  9. ezfzx

    A Interpreting Chi Squared ... backward

    OK, so, I've forgotten more statistics than my students will ever know, and I'm not too proud to ask for help, cuz I'm just blanking out on this. I would appreciate it if someone could patiently follow along and let me know what I've got right or wrong please. My understanding of the chi-sqr is...
  10. qspeechc

    I R Value in Social Sciences

    Hello everyone. I stumbled across an article in the social sciences that had a correlation coefficient of r=0.93. Being from a maths background and knowing nothing about things like social sciences, psychology, etc., is this r-value in these types of fields considered fairly strong, strong...
  11. F

    Generating correlated normals

    Homework Statement Given correlation matrix $$M = \begin{bmatrix} 1 & .3 & .5 \\ .3 & 1 & .2 \\ .5 & .2 & 1 \\ \end{bmatrix}$$ And 3 independent standard normals $$N_1, N_2, N_3$$ using cholesky decomposition A) get the correlated standard normals B) and if...
  12. N

    What is preventing me from achieving better accuracy for this delay?

    I have 2 PERFECT data of the transmitter and receiver. From 2 data, I can calculate the delay estimation: Fs = 8e6; % sample rate ... for i = 1:2 [cc_correlation,lag] = xcorr(signal2(i), signal1); [cc_maximum, cc_time] = max(abs(cc_correlation)); cc_estimation...
  13. M

    I Significant correlation, not significant coefficient

    A couple of questions today. First. I am running a panel data regression test. First I check the correlations between the independent variables and the dependent variable. these are the results. The D/(D+Em) is the dependent variable, and the independent are the 4 variables most adjacent...
  14. entropy1

    I Are entanglement correlations truly random?

    Suppose we have two truly random sources A and B that generate bits ('0' or '1') synchronously. If we measure the correlation between the respective bits generated, we find a random, ie no, correlation. Now suppose A and B are two detectors that register polarization-entangled photons passing...
  15. N

    How to calculate Time Delay Estimation?

    I have 2 data files, which links are attached below: Transmitted data Received data Those binary data are read by this MATLAB code: %% initial values: nsamps = inf; nstart = 0; %% input...
  16. A

    I Understanding autocorrelations in 2D Ising model

    I wasn't sure where to post this, I hope this was the right section. I've been struggling quite a bit with implementing an autocorrelation code into my current project. The autocorrelation as it is now, is increasing exponentially from 1 at the start of my MC run, and hitting 2 halfway through...
  17. F

    I Correlation functions and correlation length

    I thought I understood the concept of a correlation function, but I having some doubts. What exactly does a correlation function quantify and furthermore, what is a correlation length. As far as I understand, a correlation between two variables ##X## and ##Y## quantifies how much the two...
  18. entropy1

    I The mechanism of entangled particles

    First let me ask this: Consider a pair of entangled photons fired at a respective detector after passing respective polarisation filters. If a photon passes a polarisation filter, is it in a superposition of having passed and not having passed? Is the measuring device (that detects the...
  19. F

    A Physical interpretation of correlator

    Consider the 2-point correlator of a real scalar field ##\hat{\phi}(t,\mathbf{x})##, $$\langle\hat{\phi}(t,\mathbf{x})\hat{\phi}(t,\mathbf{y})\rangle$$ How does one interpret this quantity physically? Is it quantifying the probability amplitude for a particle to be created at space-time point...
  20. entropy1

    B Pseudorandomness of correlation

    Suppose we have a source of polarization-entangled photons, that fires pairs of photons in opposite directions at two detectors with orientation-adjustable polarizationfilters in front of them. Obviously, there is a correlation between the orientation of the respective filters and the joint...
  21. entropy1

    B Counterfactual definiteness and correlation

    If we assume there is no counterfactual definiteness, would that mean that measurements on entangled particles needn't be correlated, for if you don't compare the results, you just don't know if they do?
  22. entropy1

    I Macro state of a measurement device and correlation

    I have a question that seems to reflect my main concern with QM. Here it is: Consider a series of polarisation-entangled photon pairs that are sent in opposite direction to two measuring devices (e.g. at opposite ends of the universe). The measurement consists of detection of a photon after...
  23. entropy1

    I Is there a 'memory-effect' of measuring devices?

    If I'm correct, a series of with respect to some property entangled particles exhibits a correlation between several measurements of that property by means of two measuring devices. My question is: is it possible that between measurements the physical constitutions of the measuring devices...
  24. entropy1

    B Equivalence of entanglement and decoherence?

    Just taking an advance in what I want to learn someday: I understand that decoherence and entanglement are more or less equivalent. So, I take it decoherence is in principle a process of entanglement. Consider two particles A and B who are entangled. if A decoheres by interacting with particle...
  25. entropy1

    B Entanglement, correlation and randomness

    I was wondering. In this example I use polarized photons, but maybe it is applicable to electrons and spin also. We can prepare two completely unentangled polarized photons, and send them in opposite directions to two detectors preceded by a filter at particular angles. Both of them will show a...
  26. Tone L

    Correlation Coefficent

    Hello I have to variables X and Y, 50,000 in each row (a time series of 2 years). I am curious how to calculate a linear correlation between the two, for example if X decreases does Y increase or decrease. Looking for formula or a MATLAB function :)
  27. H

    Difference between 2-point and 4-point function in QFT

    As I understand it, the 2-point fnuction is for 1 particle incoming, 1 particle outgoing. The 4-point function is for 2 particles incoming, 2 particles outgoing. Is this correct? So an N-point function describes N/2 incoming particles and N/2 outgoing particles? Thanks!
  28. nikosbak

    3-point function QFT

    Homework Statement I'm working on path integrals for fermions and I came across an exercise that ask to compute the three point functions , one of that is the: $$<0|J^{\mu}(x_1)J^{\nu}(x_2)J^{\rho}(x_3)|0> $$ where $$J^{\mu}$$ is the current $$J^{\mu}=\bar{\psi}\gamma^{\mu}\psi$$. ***Can you...
  29. sheila92lala

    Correlation between a continous and nominal data in SPSS

    How do i check for correlation or test for association between a continuous data and nominal data in SPSS? My nominal data is the "type of GPS receiver" and the continuous data is "latency" in seconds.
  30. R

    Fun maths question, correlation?

    Say i m in the cinema and there are 4 seats. say the closest seat is the best view which is 4 meters away. say the further the distance away the worse the viewing quality. eg [5,6,4,9] are the distances of seats away from screen. Now lets say people sitting in front of you also effects viewing...