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

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15 views

Correlation between intertwined values [on hold]

I see a negative correlation between X and Y, that are calculated based on the same values (B and D): $X = A / (BC + DE)$ $Y = (B + D - 1) * (F+G)/2$ Consequently, I can also write: $Y = H/X + G$ ...
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5 views

Correlation computing time series data of unequal sample size

I am working on a computing a correlation between two variables X and Y. Both are time series and were recorded during the same period. 6/25/15. However X was recorded much more often than Y. ...
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25 views

Next step after principal component analysis

I have a data set that consists of different characteristics of communities. What I want to do is to see how those characteristics influence each other. As in, for example I have the income and ...
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26 views

statistics analysis to find dependence between two variables

I have a question I appreciate that if somebody can help me. I am working on hydrological model in agriculture area. At this moment I want to figure out if farmers consider the soil characteristics in ...
2
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0answers
30 views

Spearman's rank correlation has p-value zero?

It looks like R's cor.test returns p-values of exactly zero if the real p-value is very low. For example: ...
0
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0answers
9 views

Website classification using metadata features

I want to fit a model that predicts a website type according to metadata features that I manually collected, such as - Average text length, average # of pics, average outgoing links per page, etc... ...
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2answers
39 views

Linear correlation between two sets of data

I have various data sets that correspond to values (in percentage) at given time points (hours, up to 10 hours). The total number of data sets of values at given time points is 8. My question is ...
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0answers
12 views

What are the most important components of an item analysis of a MCQ exam?

I'm analyzing results of undergraduate exams that range from 60 to 100 multiple choice questions. The number of students doing any given exam ranges from ~70 to ~1000. In all cases students select ...
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18 views

Bonferroni correction for multiple testing and overlapping groups

I have allele frequency observations from a large geographic region that can be logically subdivided into smaller areas in a number of different and meaningful ways. If I were to test these ...
3
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1answer
31 views

Correlation between different Likert scales

I use a likert type questionnaire (7 point scale) in order to measure four variables: usefulness, ease of use, ease of learning and satisfaction. Hence in the questionnaire I have four different sub ...
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0answers
13 views

Standard deviation from difference between percentile [closed]

Assuming that the underlying distribution follows the normal distribution, if we are given a difference of aX (units of another random variable) between the 2d percentile and the 98th percentile of Y, ...
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27 views

Granger Causality / VAR / Negative Correlations

I have two questions on Granger causality. I feel puzzled after reading a dozen of papers on the topic and it appears to me that I need to clarify my understanding of Granger causality. Question 1 : ...
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20 views

Given a set of random numbers, generate a second set that is correlated with the first (Python?) [closed]

In simulating a system, I generate a set of random numbers: set1 = [.6, .32, .1, .59 .9, .21, ...] I want to create a second set (of the same size) based upon the ...
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12 views

Correlation with stratified data structure

I have a dataset with two stratas, the first level is called block, which represents the census block. the second level is two predetermined subgroups in each blocks, each subgroup contains several ...
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21 views

Are there any other websites which will let you compare worldwide stats for wide ranges of topics? [closed]

This is what I found after some googling and testing: http://www.tylervigen.com/spurious-correlations They only have U.S. data while I'd like to find worldwide stats. Anyway, should I need to ...
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0answers
27 views

How to determine the best correlation matrix?

Suppose I have a data series of stock returns and I am trying to determine the correlation between these two series. In the first instance, I calculate the correlation matrix of the data series as ...
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0answers
10 views

Correlation between two rasters

If I have a fire frequency rasters (with 6 possible values)(the independent variable) and a vegetation change raster ( with 3 possible outcomes)(the dependent variable) how do I test the possible ...
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1answer
26 views

Scientific P Value with adjusted R Square [duplicate]

I am running Spearman correlation between 2 variables weight and freight both being numeric. The output I have received from correlation is P value - 0.00E+000 and Rank R Squared is 0.61 and which ...
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0answers
13 views

Calculating correlation coefficients in panel datasets [closed]

I have an unbalanced macro panel dataset where the the id represents country sorted by year. I want to calculate the correlations for different groups. Suppose I have data on growth and poverty. And I ...
2
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1answer
42 views

Simulating random variables given partial distributions and correlation

After Monte Carlo simulations I obtained approximated distributions for X and Y. Now I want to add some form of correlation between them. To simulate random variables from a distribution the idea is ...
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41 views

How to test for a correlation between two variables, if the linearity assumption is violated?

I have two variables that show no linear relationship. It's not even monotonic. Does this mean that the variables are independent of each other? Can I still run a non-parametric test? Or can I just ...
2
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1answer
22 views

Does concordance correlation require data to be normally distributed?

I would like to know if the results from Device 'A' and Device 'B' are in agreement when measuring the same thing. I have 258 pairs of results. The results are interval variables and have the same ...
1
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1answer
26 views

Is it valid to average correlation coefficients in this scenario?

We have a client who manufactures materials with different surface 'roughness' characteristics, ranging from near-glass smooth to coarse sandpaper-rough. They have ten different grades of roughness, ...
3
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0answers
55 views

Is it possible to validate this claim about gun shootings and SSRIs?

We have received an interesting question on Skeptics.SE: Is there a correlation between mass-murder and use of psychoactive prescription drugs such as SSRIs? My suspicion is that this is not ...
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5 views

Predicting Vector Similarity Given Parameter for Vector Calculation

Weird title I know, let me explain. Parameter sets $a$ and $b$ are used to parameterize function $F$ to produce vectors $x$ and $y$ respectively. $G(x,y) = j$, is the jaccard index and our metric for ...
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1answer
28 views

Correlation Analysis of Standarized Testing Data

I need some insight on how to correctly analyze some data using correlations. The nature of the data and research endeavor is as follows: I have two independent samples of different sizes that ...
0
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1answer
12 views

Coefficient of determination applied to difference in means?

Assume we have one random variable X, and two groups A and B have different mean X values. Let's say we have another variable Y that has a correlation with X of 0.5. If I wanted to estimate a Y ...
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11 views

Correlations for Categorical, Dichotomous, and Interval Data

My non-parametric data consists of a categorical criterion variable with 7 levels (one that has a frequency <5) and 24 predictor variables, 7 of which are categorical (some with frequencies < 5, ...
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32 views
+50

Construct validity via SEM

It's often seen that convergent and divergent validity of a construct is checked via manifest correlations. I asked myself if such an approach can be replaced by testing a whole SEM containing the ...
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7 views

How to demonstrate connection between performance and difference between real and optimal values of the parameters

I have the data from the experiment with 140 participants. I model the process of decision-making during the experiment and estimate the values of two parameters (A and B). Then, using simulations, I ...
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35 views

Correlation between two samples of different size

I have all price quotes from a stock (to be more precisely CSAN3 from Ibovespa Exchange - Brazil) from 2010 to 2015. I was asked to get the correlation from the log returns year-by-year. This is ...
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47 views

Increasing strength of correlation through regression

I have a formula (not mine): NY/A = (Passing Yards - Sack Yards) / (Passes Attempted + Times Sacked) and this formula correlates with wins at a correlation ...
0
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1answer
49 views

How to find unknown correlation coefficients in a correlation matrix from known correlation coefficients? [duplicate]

I have a correlation matrix A given below. Here A should be a positive-definite matrix so that we can perform Cholesky decomposition of A. ...
0
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0answers
17 views

Showing that scoring system A is equivalent to scoring system B (Correlation?)

In this project, we have used scoring systems A and B to analyze the same data. Each system gives a score in 41 categories. The score distributions yielded for each category for both tests A and B ...
3
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2answers
30 views

How to know if a correlation is reliable?

I found this interesting information about different correlations. An example is that, the number of people drowned by falling into a pool correlates to number of films Nicolas Cage appeared in. This ...
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1answer
13 views

How to proceed with lagged variables and correlation matrix?

Would it be correct to report a correlation matrix with the variables not lagged when you use lagged variables to fit the model? I think that you have to report the variables that you use in the ...
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1answer
50 views

Multiple Correlation towards 2 target values

I am analyzing correlations between the driving speed of several drivers pairwise on the same route and correlations between them. ...
1
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0answers
26 views

Predictive model for Turnover - Correlation or Survival Analysis

Question 1 - I a working on developing a model to predict employee turnover. The variables that I have are age, tenure, job satisfaction, role clarity etc. Through research papers I have found the ...
3
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1answer
43 views

What is Pearson's r association strength?

I am trying to grasp the concept of magnitude-of-effect estimations, as opposed to standard null hypothesis testing procedures. According to a paper by (Snyder & Lawson, 1993) the ...
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0answers
26 views

Correlation between combinations of uncorrelated variables

If I have uncorrelated variables X,Y,Z how do I find the correlation between (X+Y) & (Y+Z)? Ps. It's a theory question: ie, I can't compute the correlation from observed instances of X,Y & ...
2
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0answers
27 views

what is the distribution of $\max\{A+C,A+D,B+C,B+D\}$, given A,B,C,D are i.i.d following distribution $f(x)$?

Given $A$,$B$,$C$,$D$ are i.i.d following distribution $f(x)$, what is the distribution of $\max\{A+C,A+D,B+C,B+D\}$,? Though $A$,$B$,$C$,$D$ are i.i.d but $\{A+C,A+D,B+C,B+D\}$ are correlated. Many ...
2
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1answer
20 views

maximal information coefficient - MIC

Since the coefficient is between 0 and 1, I would like to know if the MIC allows us to know if the relationship between the two variables are positive or negative ?
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0answers
12 views

Transpose is just the way of generalizing a dot product? [migrated]

It seems like Atb is the same as writing a * b in matrix form. 1) Why is n x 1 and n x 1 matrix multiplication undefined? 2) Is this just a generalization of the dot product? If so, is it just a ...
2
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1answer
64 views

Is it possible to compute a correlation between two variables from just means, standard deviations and sample sizes?

Is it possible to compute the correlation between two variables with just the mean, standard deviation, and sample size? If so, how would I go about it?
2
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0answers
35 views

How good is my computer aided diagnosis system vs the expert?

I have developed a systematic method that attempts to quantify the amount of disease present in medical images. E.g. % area abnormal. In my dataset, I have healthy people with no disease, and people ...
0
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0answers
16 views

Dummy regression, reference group selection, Mallows' $C_p$ criterion, correlation

I am using glm (target, formula = target~.,family=binomial) to predict binary outcome. I have 9 grouped predictors. I convert them into factors so that I can test ...
0
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1answer
33 views

Correlation between a percentage and a real number

I have two datasets, one containing the percentage of people with flu and one which has the number of searches for Tea-recipes in google. Problem is, I get different results when i choose to include ...
1
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0answers
52 views

What statistical test should I use if the relationship between two variables is neither linear nor monotonic?

I am confused. My scatterplot says that the relationship between the two variables is not linear, so I can't use Pearson's correlation and neither is it monotonic, so I can't use Spearman's ...
0
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1answer
21 views

non-parametric analysis

I have faced a problem with my data which have different disrtibution. I have some data that are scaled one so possible to do ordinary parametric analysis on them (ANOVA, Correlation, ...) and series ...
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0answers
32 views

correlation between categorical variable and itself (multiple categories)

I've got a categorical variable that people can be in more than one category of—think something like "choose your favorite color or colors". What can test for correlation between the categories? I ...