48 views

### Which correlation formula should be used when we add up many measurements of the ordinal type?

Let's say, I have two set of questions; one set is to detect depression (var1) where the response of each question is in Likert scale and another set of questions to detect hopelessness (var2) where ...
206k views

### Pearson's or Spearman's correlation with non-normal data

I get this question frequently enough in my statistics consulting work, that I thought I'd post it here. I have an answer, which is posted below, but I was keen to hear what others have to say. ...
27k views

### How do you estimate correlations between ordinal and binary data in SPSS?

I'm struggling with my lab report. I have a questionnaire which contains Likert responses (1-7) as well as questions that require only yes or no answers. I want to see if there is a correlation ...
381 views

### How to choose a correlation measure when Pearson is close to 1 and Spearman close to -1?

I have two large datasets from nonlinear control systems. I am trying to correlate the error with the control action taken. If the error is plotted as fx and the control action as fy we end up with ...
2k views

### Normal Distribution for Pearson Correlation

I have read that the variables must be approximately normally distributed to apply Pearson correlation; However, I came across this answer here that they dont need to be, so I am confused about ...
120 views

### What metric to calculate correlation between average user ratings of products?

What's the best method to see if there's a strong correlation between two types of ratings on a product level (product $1, 2, \dots, n$) where each product has ratings of type '$a$' and '$b$'? For ...
2k views

### Pearson correlation between a variable and its square

Here is my R code to get familiarised with Pearson's correlation. I generate values of $X$ from 1 to 100, then find the correlation between $X$ and $X^2$: ...
44k views

### Spearman's or Pearson's correlation with Likert scales where linearity and homoscedasticity may be violated

I am wanting to run correlations on a number of measurements where Likert scales were used. Looking at the scatterplots it appears the assumptions of linearity and homoscedasticity may have been ...
14k views

### What could cause big differences in correlation coefficient between Pearson's and Spearman's correlation for a given dataset?

The Pearson's coefficient between two variables is quite high (r=.65). But when I rank the variable values and run a Spearman's correlation, the cofficient value is much lower (r=.30). What is the ...
965 views

### Should I use Pearson or Spearman correlation?

I have to know the correlation between 2 variables (bivariate distribution). None of them are normally distributed, so I assumed that I should run Spearman's correlation, which gave me a correlation ...
998 views

### Pearson and Spearman correlations [duplicate]

I'm having a problem with choosing between Pearson and Spearman correlation. I'd like to understand clearly why I should use one or the other. I have read the questions already asked here about this ...
42 views

### Correlation indexes in medicine

My father is a doctor and he asked me to find out if there is a correlation in two sets of data he collected, one concerning the age of his patients and one concerning the value of a medical exam I ...
3k views

### Correlation of two interval scaled variables

I have two variables A and B of interval scale type. A is the birth year of a person and B is the number of years spent at university. What method would you recommend to measure the correlation?