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

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1answer
17 views

Multiple regression with correlated variables

I am trying to do multiple regression analysis of a continuous health variable (yval) keeping age, gender, height (cm), weight (kg) and waist (cm) as predictor variables for a database of about 7000 ...
0
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0answers
7 views

test of correlation among binary variables prior to running logistic regression analysis

I am running a logistic regression analysis with binary variables on SPSS: dependent variable: preterm birth (Y/N) independent variables: hypertension (Y/N), diabetes (Y/N), C section (Y/N), ...
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2answers
28 views

Covariance greater than Variance?

It is straightforward to verify that for two random variables $X$ and $Y$ with variances $\sigma^2_X \neq \sigma^2_Y$, we have that $$\Big|{\rm Cov}(X, Y)\Big| \leq \max\{\sigma^2_X,\, \sigma^2_Y\}$$ ...
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2answers
25 views

If $E[Y|X]=a$ for some constant $a\neq 0$, then does $cov(X,Y)=0$?

I'm currently working on the following problem: Q: If $E[Y|X]=a$ for some constant $a\neq 0$, then does $cov(X,Y)=0$? Now I am quite lost as to how to do this problem as the question does not ...
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1answer
17 views

Non-additive property of correlation coefficients

Sorry if my question is quite basic! What does it exactly mean? Correlation coefficients are not additive!
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0answers
4 views

How to test correlation of two variables from four repeated measures of each one among four groups

I have four plots from where I took a measure of two indicators of population abundance (as continuous variables) throughout four surveys (say, at spring 2010, fall 2010, spring 2011, fall 2011). So, ...
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0answers
20 views

Threshold for Pearson correlation for hypothesis testing [on hold]

How to determine threshold for Pearson correlation coefficient which reduces type 1 and 2 error and and can be used whether the sample is correlated or not?
0
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1answer
37 views

Can I use z-scores to compare data measured in different units?

I am trying to compare the accuracy of two different methods of estimating biomass. This data is in the form of percentage cover (and is arcsine transformed). I also have the real biomass values, ...
1
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1answer
21 views

Is it true to say that methods are correlated?

I'm comparing a set of methods. Each method generates a list of observations, then I compute the correlation between the observations of the methods. Is it correct to say that I'm checking the ...
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0answers
8 views

Multiple Imputation in R on data with repeated measurements

I am working with an occupation cohort exposed to radiation and have a dataset containing a number of variables on each worker, including their job title, year of birth, radiation exposure level, and ...
1
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1answer
33 views

Using correlations for “explained variation”

I have measured lifetime offspring production in an insect by taking measurements of offspring production at intervals (once per week for 9 weeks). Total lifetime reproductive success is then the ...
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0answers
12 views

How to compute a really large correlation matrix in R using WGCNA library? [on hold]

How to compute a really large correlation matrix in R using WGCNA library? ...
1
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0answers
30 views

Similarity vs Correlation [on hold]

What is a difference between similarity and correlation? What are the most common similarity functions (excepted cos similarity) and could the value of similarity be between $[-1,1]$ or it should be ...
0
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0answers
21 views

Annotation of FDR vs. pvalue plot

I have calculated spearman correlation for gene pairs in 2 microarray datasets . Then, I have used FDR adjustment for p-values. Plotting FDR vs. -log10(pvalue) is surprising. Is the result realistic ...
5
votes
2answers
35 views

How to get p-values or confidence intervals for pearson correlation coefficient when the sample is small and potentially non-Gaussian?

The p-values provided by the built-in Matlab and Pylab Pearson correlation functions are stated to be inaccurate for small sample sizes, or when the samples are not normally distributed. The python ...
3
votes
1answer
74 views

Is there any difference between $r^2$ and $R^2$?

The correlation coefficient is usually written with a capital $R$ but sometimes not. I wonder if there really is a difference between $r^2$ and $R^2$? Can $r$ mean something other than a correlation ...
6
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3answers
166 views

How to rearrange 2D data to get given correlation?

I have the following simple dataset with two continuous variables; i.e.: ...
0
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0answers
27 views

i have 264 variables. i want to pick up the three variables that least correlate [closed]

i am using satellite image having 264 bands.. i will consider all bands as variables . i want to pick up the three bands that have the least correlation to display on RGB of the monitor screen
5
votes
1answer
57 views

Asymmetric measure of non-linear dependence/correlation?

I am definitely not a statistician/mathematician so feel free to tell me I'm an idiot if I am. As far as I can tell from my Wikipediaing all of the main measures of dependence are symmetric and ...
0
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0answers
15 views

How to generate a list of intercorrelating items in R language? [on hold]

I could build a correlation matrix from microarray experiment total intensity values. However, I can`t visualize 365X365 data matrix and I need to generate a list of mutually correlated genes from ...
0
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2answers
26 views

Emphasize a link between two predictor variables (Machine Learning)

I am creating a machine learning application which will utilize logistic regression (though I haven't ruled out bayesian regression). I have multiple predictor variables that I believe to be ...
3
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2answers
54 views

Correlation between two ordinal categorical variables

What is the best statistical test for investigating if there is any correlation between 2 categorical variables? both are satisfaction scores: 1-First variable is: "Overall satisfaction with the ...
1
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0answers
42 views

Statistical method to prove inverse relationship between class size and student achievement

A hypothesis states that there is an inverse relationship between class size and student achievement. With data records about class sizes and grades of its students at a certain school, we would like ...
1
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0answers
18 views

Correlation of two means, with known variance

I would like to estimate the correlation of two variables, A and B. For the first variable I have made three independent ...
0
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0answers
22 views

correlations between characteristics of students and success in college courses

Students have been psychologically surveyed and characterized in terms of emotional and social factors. The hypothesis is that there is a positive correlation between emotional and social factors and ...
3
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0answers
57 views

Draw balls from two different binomial distributions. What $r^2$ do you expect to find?

We have $N$ buckets in which we will put some balls. Before that, the buckets are split into two groups, group $A$ and group $B$. The number of balls that we will put in each bucket is drawn from a ...
0
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0answers
55 views

How to apply a Gaussian filter to co-ordinate data

I'm working on a project to investigate the correlation of surface finish and face sealing effectiveness. I have a trace of the surface of my seal and the next step is to apply a Gaussian filter to ...
0
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4answers
55 views

Interpreting high p value and low correlation value

I am trying to run regression on financial data in R. I am new to regression analysis so I am finding it to difficult to interpret certain scenarios. I have the code as follows: ...
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0answers
8 views

Correlation between response and predictor due to variable sharing

Assume a process which acts on two entities, $a$ and $b$, to result in a further entity, $c$. It is considered that the amount of entity $a$ determines the amount of entity $c$ such that entity $a$ ...
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0answers
18 views

Correlation with aggregated data

I have a question about calculating correlations with aggregaged data and I would be really happy if someone could answer my question. I have a population (not a sample) composed by more than ...
0
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0answers
22 views

Compare to sets of correlations coefficients

I have two matrices, A and B, of the same size. Each row of A corresponds to a row of B. Theory predicts that some rows of A will negatively correlate with corresponding rows of B. I am interesting ...
0
votes
1answer
25 views

Correlation between ordinal and average values

I'm trying to understand whether the number of words used to title a problem are related to the time used to solve that problem. In order to do this, I have derived two vectors from my data-set, one ...
3
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0answers
41 views

Partial correlation and multiple regression controlling for categorical variables

I am looking through the linear association between variable $X$ and $Y$ with some controlling variables $\mathbf{Z} =(Z_1, Z_2, Z_3, \dots)$ One approach is to do a regression $E(Y)= \alpha_0 ...
5
votes
2answers
118 views

How to use Pearson correlation correctly with time series

I have 2 time-series (both smooth) that I would like to cross-correlate to see how correlated they are. I intend to use the Pearson correlation coefficient. Is this appropriate? My second question ...
0
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0answers
10 views

How do I blot out too big p-values in a correlation matrix comparing two different subsets? [migrated]

I'm doing correlation matrixes in R. I love the corrplot package, because of its ease of use and pretty graphics. All the examples on the help page have been done using mirrored rows and columns, but ...
1
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1answer
64 views

Pearson's or Spearman's?

We are doing a lab report comparing attachment scores and their effect on trust scores. We have been told to do correlations followed by linear regression to get rid of confounders. However, we have ...
5
votes
1answer
63 views

when can I say there is a relationship between events?

I am analysing a weather data for a computer science course using hadoop.I am taking away all the weather related issues out of the analysing and just looking strictly at it in the eyes of statistics. ...
2
votes
1answer
21 views

Expectation, Variance and Correlation of a bivariate Lognormal distribution

If $Y \sim N(\mu,\sigma^2)$ is normally distributed, then $X=\mathrm{e}^Y$ is lognormally distributed. To get the log-$\mu$ and log-$\sigma$ of this lognormal distribution you calculate $$\sigma^2 = ...
4
votes
1answer
30 views

Estimate an overall correlation from the correlations within subgroups

Assume that you are working with variables $x$ and $y$ divided into groups two groups, $g_1$ and $g_2$. You know the following information: The number of people within groups $g_1$ and $g_2$, ...
2
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1answer
22 views

Partial correlation to check whether C drives a normal correlation between A and B

Say I have two scores from a certain population, A and B, that are correlated. Say that I also have a third variable from that population, C, and I now want to see if the partial correlation between A ...
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0answers
39 views

Comparing two dataset using several different tests

I have several datasets of about 10k items. I have to compare all of them with the reference dataset, and draw some conclusions as to which is the best. Let's say I have no information on the shape ...
0
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0answers
11 views

mat.regress/set.cor [migrated]

I am having a problem with the function mat.regress in the psych package that I was hoping someone would be able to give guidance on. I have a correlation matrix that is [76,76] with the first ...
1
vote
1answer
40 views

Correlation choice when attribute values are given in intervals

I am trying to find the correlation between two continuous variables but the values of one of them are originally given in intervals ([1-5] ,[6-9],...). What is the best approach to deal with this? ...
0
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0answers
12 views

Comparing 3 data sets with multiple variables for agreement

looking for some advice on the best statistical tool to assess agreement between 3 different data sets measuring different variables (i.e. what is the agreement between results from group 1 across 18 ...
0
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0answers
6 views

lme dependence and correlation test, the differences and the similarities

I am not statistician and trying to compare two data sets, both real numeric. I look for lme dependence and for correlation test. While I found significant correlation between these two data sets, the ...
2
votes
1answer
47 views

How to find similar users by looking at their votes in a community website?

I run a community website with ~1600 users who made 750 000 votes on 100 000 posts. The votes are made on the Likert scale, i.e. from 1 to 5. I want to help users find like-minded people. After some ...
4
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3answers
80 views

Hypothesis test for correlation between Gamma random variables

I have two Gamma random variables. I need a hypothesis test to detect a possible correlation between them.
0
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2answers
48 views

What is the relationship between a regression coefficient and a correlation coefficient?

One might expect there to be a formal relationship between a regression coefficient and a correlation coefficient (at least intuitively). Does this relationship change if the distribution of the data ...
0
votes
1answer
10 views

How to run correlation test between each value of an ordinal variable based on a dependent continuous variable values?

Hi i have two data sets on which i need to run statistical test and correlation analysis. column A has ordinal values ranging from 1 to 7. column B has nominal values A, B, and C. column C has ...
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0answers
14 views

Measure the Ranking of Variables

What I want to do is compare the ordering of variables determined by the ranking of each variable. For example: Say, I have a rating system that is made up of 5 different ratings - Excellent Good ...