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A measure of the degree of association among a pair of variables.
1
vote
Accepted
Pearson Correlation and Linear Combination
$\newcommand{\Cov}{\operatorname{Cov}}$
Let $u_1=ax+cw$ and $u_2=by+dz$. Then we have
\begin{align*}
\rho(u_1,u_2)
&=\frac{\Cov(u_1,u_2)}{\sqrt{V(u_1)}\sqrt{V(u_2)}}.
\end{align*}
Let $C=\dfrac{1}{\sq …
0
votes
Correlating noisy time series with a phase difference (lag)
Here's some Python code I wrote once to test out the max correlation method. … 0][1]))
print("Now we find max correlation coefficient:")
# Create a vector of correlation coefficients. …
3
votes
Accepted
Does significant correlation imply at least some common underlying cause?
The usual "post hoc ergo propter hoc" fallacy is the fallacy that says correlation always implies causation, or even that you can infer causality. This is still a fallacy. … However, if you add another condition to the correlation - namely, that of mechanism - then you get Reichenbach’s common cause principle: "No correlation without causation." …
2
votes
If 2 variables are dependent, then there always exists a 3rd variable that causally influenc...
This is the reason the aphorism, "Correlation does not imply causation" ought to be replaced with Reichenbach's principle: "No correlation without causation." … Or at least, "Correlation usually implies causation."
Causation is more fundamental than correlation, and it's certainly much easier for humans to reason about than correlation. …
3
votes
Is there any truth to the phrase "statistics mean nothing to the individual"?
I agree with the other answers, but I would like to add that in the New Causal Revolution, particularly with the highest level of reasoning - the counterfactual - it is possible to reason about indivi …
5
votes
Accepted
Difference between Covariance and Mutual Information
You can interpret the correlation as a measure of how well a straight line (linear relationship) fits the data. If you have a correlation of $\pm 1,$ then it is a perfect linear relationship. … You can introduce a new feature, call it square-of-velocity, and then do a correlation with that new feature. …
1
vote
1
answer
573
views
Correlation Coefficient Squared is Less Than or Equal to One
Let $\rho$ denote the correlation coefficient of $Y_1$ and $Y_2.$ Using the inequality
$$[E(Y_1Y_2)]^2\le E\!\left(Y_1^2\right) E\! …
4
votes
1
answer
780
views
Correlation Coefficient for Hypergeometric-type Distribution
Find the correlation coefficient for $Y_1$ and $Y_2.$ (Let $p_i=N_i/N$ for
$i=1,2,3.$)
This is Exercise 5.110 in Mathematical Statistics with Applications, 5th Ed., by Wackerly, Mendenhall, and Scheaffer …