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A measure of the degree of association among a pair of variables.

1 vote

Sum of Products of Z scores - why does this =( n-1) in a straight line

like a homework question (and I could be wrong), I will start by only providing a hint: There is a concise relationship between the product of the $z$-scores for two variables (say $x$ and $y$) and the correlation
Gregg H's user avatar
  • 6,064
2 votes
Accepted

Can I multiply two correlation coefficients?

In path model analysis, the correlation between two variables connected via a third variable is calculated in this fashion. … The total correlation would be this value added to the values from any other valid paths in the model. …
Gregg H's user avatar
  • 6,064
1 vote

Interpreting results of regression of variable with residuals from previous regression

of $u$ and $v$ to calculate the partial correlation.  … If you take the correlation of $u$ with $s$, you obtain the semi-partial correlation.  …
Gregg H's user avatar
  • 6,064
0 votes

Distribution rhino and elephant, what test to use?

I am not certain a correlation is the best approach. I am making a number of assumptions on the nature of your data, so this approach may not be correct. …
Gregg H's user avatar
  • 6,064
5 votes
Accepted

Test the difference between two (genetic) correlations, when only standard errors and z-stat...

I believe you are referencing the Fisher's z-transformation (as if you were referring to a test statistic for the correlation, it would be a t-ratio). …
Gregg H's user avatar
  • 6,064
5 votes
Accepted

How to interpret a polychoric correlation?

Let me provide my answer using the tetrachoric correlation (which is the polychoric correlation when you have two dichotomous ordinal variables). … Now, if we assume the same thing for our 2nd variable, say $y$ (with an underlying $\eta$ variable), then we call the correlation of $\xi$ and $\eta$ the tetrachoric correlation. …
Gregg H's user avatar
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0 votes

Why correlation is considered an effect size?

The correlation you reference in your question is between the independent and dependent variable. … However, you could also reference the correlation between the dependent variable and the predicted values for this variable using the independent variable(s), $R= \text{cor}(y,\hat{y})$. …
Gregg H's user avatar
  • 6,064
3 votes

Is homoscedasticity an assumption for Pearson's correlation?

But, Pearson's correlation is a defined quantity. As such, it is what it is, and the value itself does not have any assumptions. … But, the real reason people might argue that this is an assumption is because the correlation is often used as a measure of the linear relationship. …
Gregg H's user avatar
  • 6,064
0 votes
Accepted

Testing correlation coefficient of two bivariate gaussian

If you wish to test if two correlations from two samples for independent pairs of variables are different from each other, the null hypothesis statistical test (NHST) appropriate for this would be the …
Gregg H's user avatar
  • 6,064
1 vote

Testing correlation coefficients from two bivarate poisson

The reason for this is that the distribution of the correlation coefficient is nearly normal with the transform. …
Gregg H's user avatar
  • 6,064
1 vote

How to assess the absolute strength of a correlation between two multifactorial variables wh...

It is possible to run a CFA where there is a non-zero correlation estimated between the two latent factors. … Assuming these values are all from a population with zero correlation, some positive and negative small values would be expected. …
Gregg H's user avatar
  • 6,064
2 votes
Accepted

How to interpret zero order correlation and higher order partial correlation?

If you look only at the direct effect of $x_3$ on $y$, you will see a strong positive correlation. However, this ignores the other variables that may/may-not be influencing $y$. … Conceptually, if you take the residuals from predicting $y$ form everything by $x_3$ and the residuals from predicting $x_3$ with everything (but $y$, of course), these residuals have a negative correlation
Gregg H's user avatar
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0 votes

Bonfferroni correction of correlation p-values. What's my k?

(Not sure why you would want to test if the aggregated sample correlation matrix on its own...but if you did, multiple by 3 instead of 2.) … If you have three times points, then you probably would want to assess the correlation for each scale at each pair of time points. …
Gregg H's user avatar
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1 vote

Creating a popularity index from multivariate data

I am going to propose a very pragmatic protocol based on the following rationale: a high number of high average ratings should be ranked very high a low number of high average ratings probably should …
Gregg H's user avatar
  • 6,064