Questions tagged [fisher-transform]

Fisher's z-transform is a transformation that is applied to the correlation coefficient, r, for use in hypothesis testing & constructing confidence intervals.

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Why is fisher transformation necessary?

I read that the correlation coefficients have to be converted by using a fisher-transformation when one wants to test their significance (like here When is Fisher's z-transform appropriate? ). I ...
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Comparing regression/correlation values within-subjects? Repeated Measures ANOVA afters Fishers Transform?

I was interested in the most appropriate way to assess whether there is a difference in the R values from a regression analysis in a repeated measures design. I transformed my R values using a ...
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Significance testing correlations with few data-pairs: how necessary is Fisher Transformation? Alternatives when it appears innapropriate?

Apologies for large post/question: I presented 116 subjects with displays of frequency distributions for 2 groups of data and asked subjects to provide subjective ratings on a 10 point Likert scale ...
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Test for unequal correlation coefficients inflates Type I error for non-uniform sample distribution. How to correct?

Aim I'm studying the hypothesis test which estimates the probablility of the null hypothesis: The difference between two correlation coefficients is 0. More exactly, I deal with the question ...
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Simple mean or weighted mean of Fisher z-transformed correlation coefficients

I need to perform the average of a set of correlation coefficients $\rho_i$ with $i=1,\ldots,m$. I follow the standard prescription: apply the Fisher z-transformation to my $\rho_i$ ($z_i$ are the z-...
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Validity of Fisher transformation on autocorrelations?

I'm doing some analysis in which I have to determine if the autocorrelation in one sample is greater than that of another sample. Someone suggested I use the Fisher transform for this purpose, but, ...
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1answer
31 views

How to calculate Mean Sample-Based Reliability Estimates Used for Analyses

I am conducting a meta analysis of Pearson's r , of correlations presented between test scores and job performance ratings. I need to present an uncorrected effect size and an effect size corrected ...
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1answer
36 views

Average sample size of two fishers z correlations

I am conducting a meta analysis of Pearson's r correlations. As there are two correlations , sometimes three , for the same study and dependent variable I have averaged the correlations via fishers z ...
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50 views

Averaging of two or more standard erros

I have calculated two standard errors for two fishers z correlations from the same study , both measuring the same variable. Is it acceptable for me to average the two standard errors into one? If so ,...
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What is the name of this random variable?

Let $X \sim \text{Normal}(\mu, \sigma^2)$. Define $Y = \frac{e^X -1}{e^X+1}$. The inverse transformation is $X = \text{logit}\left(\frac{1+Y}{2}\right) = \log\left(\frac{1+Y}{1-Y} \right)$. By the ...
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Fisher Z transformation vs T-Test in cross sectional correlations

I want to compare the correlations of stock related measures. According to the paper referenced below, time series can be compared for statistically different correlations with the Fisher Z ...
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Fishers-R-to-Z - published study reporting value I can't replicate

I am reading a paper that reported a significant difference in correlation between age and some measure between groups. It looks like they calculated the Fisher's-R-to-Z wrong? I wonder if someone ...
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Fisher z test to compare correlations in a time series

I am running an analysis (in SAS, using proc corr fisher). http://core.ecu.edu/psyc/wuenschk/docs30/CompareCorrCoeff.pdf I basically want to know how different the correlations are on a daily basis ...
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Doing the equivalent of a dependent t-test on a sample of correlation coefficients

I’m doing an analogy of the following study. I take participants etc. and show them a picture of man 1 and have them rate his attractiveness and rate his intelligence just from his picture. I then ...
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175 views

fisher r to z test with different number of observations between variables.

Is there a way to test whether the correlation coefficient between two variables with a shard third variable is significantly different, if the sample sizes are different? Here is the case, ...
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Can someone explain the Fisher transformation and why it is used in layman's terms?

I am writing a paper on comparing different business cycles and have calculated bilateral correlation coefficients between individual countries and the overall aggregate. I have read in some of the ...
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1answer
696 views

Reporting Fisher-transformed Pearson's correlations when the magnitude of difference is relevant

My field regularly demonstrates a certain type of result with pairwise Pearson's correlation matrices between predicted and measured data. As soon as such correlations become high, Fisher-transforming ...
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Fisher R-to-Z transform for group correlation stats

I have independent correlation coefficient measures for each subject. I would like to test whether the correlation coefficient of the group is significantly different from 0. My understanding is ...
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219 views

Is Fisher's z transformation necessary when comparing the variances of correlation coefficients?

I am working on functional connectivity between brain regions, where functional connectivity is represented by the Pearson correlation coefficient between the time series (fMRI) of brain regions. I am ...
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405 views

Significance testing between two mean correlation values

I have collected 50 data points from 9 individuals for 4 variables, say, a,b,c,d. For each individual, I correlated ab and cd using a Pearson correlation. Aim: I would like to test whether across ...
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Difference Between Two Correlation Coefficients - questions

I’m working on an exercise to check if a difference between two correlation coefficients is significant. However, I have certain doubts after I did some reading about the topic. My data consists of 2 ...
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1answer
623 views

Averaging correlation coefficients

I am calculating Spearman correlations multiple times between individual data vectors that are not necessarily of the same length. So for example, ...
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637 views

Statistical significance test for averages of correlation coefficients

My setting looks like that I have several subjects $i$ (let's say 5) and for each subject I measure the lists/vectors $A_i$, $B_i$, $C_i$ and $D_i$. Then, for each subject $i$, I calculate the ...
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What is Bartlett's theory?

This neuroimaging paper has been cited thousands of times. In it, a method is proposed for computing the correlations among several seed regions and all other brain voxels. Part of this method ...
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153 views

Confidence interval for correlation

I know the confidence interval of an estimated correlation can be calculated after performing Fisher transformation. But I never figured out why. I also couldn't find the explanation online. Can ...
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701 views

Bootstrap confidence intervals

I write to you for 3 questions. I want to calculate confidence intervals on different measures of association (Pearson's correlation coefficient, Cramer's V and the Eta-square). I will make the ...
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Special case of Fisher Z for comparing two correlations

I'm a statistical consultant, one of my clients requested something I haven't heard of before: She wants to compare the correlation between X and Y (two ratio scaled variables) before an intervention, ...
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1answer
8k views

Fisher's z-transform in Python?

I want to test a sample correlation $r$ for significance ($n=16$), using p-values, in Python. As I have understood from this question, I can achieve that by using Fisher's z-transform. Is there a ...
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346 views

Calculating CIs for $\eta^2$ via Z scores - sample size?

In the thread Confidence Interval for $\eta^2$ it was proposed that if only limited statistics are available (in my case, F, df1, df2, means), one could calculate the 95% CI for $\eta^2$ by: ...
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Significance of average correlation coefficient

Disclaimer: if you find this question to be too similar to another one, I happy for it to be merged. However, I did not find a satisfactory answer anywhere else (and do not yet have the "reputation" ...
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411 views

Testing significant difference between two determination coefficients $R^{2}$ for two PLS-based structural equation models

Two structural equation models were tested (one was based on a sample with 199 individuals and the second one on a sample with 93 individuals). The aim was to test whether the results of the first ...
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When is Fisher's z-transform appropriate?

I want to test a sample correlation $r$ for significance, using p-values, that is $H_0: \rho = 0, \; H_1: \rho \neq 0.$ I have understood that I can use Fisher's z-transform to calculate this by $...
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2answers
534 views

How to Test the Difference between 2 Sets of Pearson Correlations?

Suppose I have two sets of Pearson correlation coefficients -- call them set A & set B, and they are of the same size. How do I systematically compare the correlations in A against B? E.g., I want ...
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593 views

Statistical significance of increase in correlation

I have a sample with some individuals, and also three variables measured for each individual, let's say $A$, $B$ and $C$. There is a mild correlation between $A$ and $B$ and a mild correlation ...
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Spearman's rank correlation for a beginner: Sample size and Interpretation

I am a computer scientist performing research, which includes calculating the Spearman rank correlation of two lists, one ranked by a human, another by a computer program. I have the following ...