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Questions tagged [wilcoxon-signed-rank]

Wilcoxon signed-rank test is a non-parametric rank test to compare two paired samples, whether values in one are bigger than in the other. Can also be used to compare one sample to a fixed value. [The test NOT to be confused with the `sign-test`].

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Potential problem in using paired t-test or Wilcoxon if the two samples consist of multiple draws from same group?

I have an experiment that works loosely works as follows: There are ten subjects in each treatment. There are two treatments, A and B. Each treatment has 8 rounds. In each round, each subject is ...
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Comparing the performance of two algorithms with Wilcoxon Signed-Rank Test

I have two algorithms A and B which have to compute a solution to some problem. Each solution is given some objective value ...
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Wilcoxon signed rank test - interpretation

I have 6 dependent variables that were measured on a 5 point Likert scale (treated as interval here). I want to test if their means differ significantly from the midpoint 3. As the normality ...
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39 views

Is my interpretation for Wilcoxon Signed Rank test correct?

I ran a wilcoxon signed rank test on paired samples where the outcome variable was a test score. The samples were paired by as siblings (younger and older sibling). I have a problem interpreting the ...
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How does Normal approximation work when ties exist for Wilcoxon Signed rank test?

I ran wilcox.test() in R (outcome variable was a test score and the data was paired samples) and got a warning message saying that it cannot generate a p-value for tied values. I saw the R document ...
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23 views

Pseudo median from Wilcoxon signed rank test larger than sample median?

I am left wondering, why I can be in a situation where the pseudo median (population estimator) of a Wilcoxon signed rank test, can be larger than the simple differences between sample medians? I am ...
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126 views

Paired or unpaired t-test and Wilcoxon signed rank test?

I am having a conceptual problem, of not being able to grasp whether my data is paired or unpaired. I have to test for the mean and median differences between two sets of data: SBP and GICS (see ...
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Wilcoxon rank signed test, paired or non-paired test?

I have been trying to figure out, whether or not I should use a paired or a non-paired test. My question comes from the fact, that I am trying to get the pseudo median, in order to say that SBP is [x] ...
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48 views

Wilcoxon signed rank test - help on interpretation of pseudo median

I am performing a Wilcoxon signed rank test in R, for two paired samples, where I have used the following: ...
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53 views

Wilcoxon signed rank test, getting a numerical media difference instead of p-value?

I have been running the Wilcoxon signed rank test, where my output is a p-value. Now, the p-value interpretation I am confident in, but I read in a paper that the authors reported the: The Wilcoxon ...
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23 views

Bonferroni for Wilcoxon signed rank?

I conducted a survey that asked participants to rate their level of agreement on a 5 point Likert scale with nine items (1=strongly agree, 5=strongly disagree). Hence, a mean score of 3 would mean ...
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Paired samples with various ordering in observations, signed rank test?

I have a small number (10) of samples to analyze The idea is to measure the impact of two surgical procedures, A and B. In my population, I have people who did first A, and then B, and other people ...
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31 views

Wilcoxon - one sample abnormal stock returns

I got a dataset with abnormal stock returns for around 400 securities and i need to find out if they're statistically different from zero. They don't follow a normal distribution, so i would like to ...
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Wilcoxon signed-rank test for paired and repeated measures data

I have a dataset with 45 participants, each with 1-7 datapoints/observations (126 total observations). Each of these observations represents a window of time in which two different methods attempt to ...
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Paired Wilcoxon signed rank test-compare median

I have been comparing driving behavior before and after a technological intervention for a specific group of people. My data is far from normal hence I have used paired Wilcoxon signed rank test. If ...
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58 views

Can a Wilcoxon signed rank test be applied on dated data?

I have data for military male and female orders for types of clothing purchased from 2012 to 2018 (below is a very simple example - most of the data is one item purchases). If I look at one type of ...
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38 views

P-Values in Wilcoxon test

I have a question that if a p value less than 0.05 in wilcox test means that the two data are significantly different and the p-value of 1 means that are exactly same, then what is the meaning of a p-...
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Is it correct that JMP has Mann-Whitney U for comparing more than 2 unpaired groups (instead of Kruskal-Wallis)?

To the best of my knowledge, the Mann-Whitney U test (also called Wilcoxon-Mann-Whitney) is for comparing only two unpaired groups, while the Kruskal-Wallis test is used for comparing two or more ...
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How do you perform Wilcoxon matched-pair sign-rank test in Stata using a grouping variable? [closed]

I'm performing a diagnostic method comparison study in which I have 2 groups; one assessed using the experimental method, and one assessed using the standard method. These groups are matched, with 3 ...
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Violating the assumptions of one sample t-test and wilcoxon's sign test

As far as the background of my research is concerned, I developed a framework for sustainability management in organizations through a systematic review of literature and sustainability reports. That ...
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Comparing changes in pre-post count results for two cohorts

Thanks in advance! I have a pre-post analysis Of cases and controls. The outcome variables of interest are emergency room visits and hospitalization visits - both rare occurrences with median = 0 ...
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34 views

How to run Friedman test correctly across three sets of questionnaire data divided into sub-groups?

I am trying to evaluate the usability of three prototypes of an application and want to see if there is a significant difference in terms of usability. For this I have collected responses from users ...
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Post hoc for wilcoxon multiple tests

I have a database of brain MRI acquisitions of 20 subjects at two time points. I have elaborated the signal with multiple models. For each model, I have estimated 4-6 parameters maps. At the moment I ...
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1answer
39 views

Different results from wilcoxsign_test - which test to use?

I am running a wilcoxsign_test from the coin-package and I get different results depending on whether I split my data or not. My data is a data.frame with 3 columns: "Proband", "Treatment", "Mdev". ...
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How to remove pair-wise comparisons that are affected by a batch covariate in pairwise Wilcoxon test

I have a dependent variable that is grouped by an independent.variable (with 3 factor levels) and I want to calculate pairwise comparisons between the groups of the independent.variable. However, I ...
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42 views

NASA TLX Analysis

I am trying to analyze a NASA TLX. The NASA TLX is the de facto standard for subjective workload task load. In my experiment (n=27), participants drove a track in a driving simulator while ...
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Imposing orders on distributions based on Wilcoxon test

I am trying to figure out part of a text I am reading about non parametric tests. In there it is stated that: The fact that the output of a rank test is driven by the probability that a value ...
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Wilcoxon Signed Rank Test in Python (Reporting Siegel's T vs W?)

While using the Wilcoxon signed rank test in scypy over a subset of populations, I noticed that my test score was reported as zero for an array of differences whose distribution of medians is heavily ...
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216 views

R: coin::wilcoxsign_test() distribution = “exact”

In a repeated measure design, I have two measurements for one variable for N=5 subjects. I am interested in assessing whether the distribution of the differences between the two measurements is ...
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46 views

One-tailed test for comparing paired dichotomous responses

Given reference samples $R_i$, I have two dichotomous responses $X_i$ and $Y_i$ I wish to compare. Each dichotomous response (relevant vs. irrelevant to the reference $R_i$) is generated by an ...
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How do I report a Wilcoxon-signed rank test if the medians are the same?

I have data comparing 2 likert-scale answers (1 to 7) where the p<0.05 but the medians are the same. I'm trying to report this in a table. My instinct was to report this similar to a t-test, with ...
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1answer
437 views

How to graph Wilcoxon test power R

I've been trying to calculate and graph the correspondent power for the wilcoxon signed test and haven't had any luck. I tried simulating two normal distributed samples, apply the wilcoxon test and ...
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394 views

Wilcoxon test with multiple testing: which correction for p values?

Please, I'm not very confident in statistics, and I'm trying to respond to a reviewer for a paper on the following issues: In my experiment I observed 15 babies during a test where they were free to ...
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252 views

Interpretation of the t.test and Wilcox.test in R

I got two distribution which are not pairs. It's difficult to say that they are also from a normal distribution because they have different length. The distributions of the vectors are, for gas: <...
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407 views

Wilcoxon signed-rank test null hypothesis statement

I performed a one-sided Wilcoxon signed-rank (WSR) test. I had a matched pair of continuous random variables, say $X_1, X_2, ..., X_n$ and $Y_1, Y_2, ..., Y_n$. For my system, it is safe to assume ...
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multi-level Wilcoxon analysis

The question was originated from the paper [1] Table 3 [2], for every species, there was a data frame with two column: disease categories and the conservation index. Conservation index is numeric. The ...
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1answer
90 views

Wilcoxon signed rank test independence assumption

Let us say we perform Wilcoxon signed-rank test on paired samples $x_{1,i}$ and $x_{2,i}$. I am trying to understand the independence assumption of the test. My questions are: Which quantities must ...
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1answer
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What is the appropiate Non-parametric test for study with 3 conditions?

The IV has 3 separate conditions & the DV measures Pre & post scores (ultimately to see what condition has the biggest effect on the scores - if there is any). The data is non-parametric- ...
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357 views

Scipy Wilcoxon test: rejection direction

One-sided test Lets say I want to compute one-sided wilcoxon test: R: ...
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2k views

How to deal with ties when conducting Wilcoxon signed rank test?

I have a paired data with a small sample size of 21 and I'd like to conduct Wilcoxon signed rank test using R. wilcox.test from the base stat package gives results ...
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102 views

Paired t-test or Wilcoxon signed sum rank test for a slightly skewed data with a small sample size of 21? [duplicate]

I have a paired sample data with n=21. The two values V1 and V2 are from two different time points for the same group. I want to see if there is any improvement/reduction in values at time 2(V2). Of ...
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1answer
163 views

The Wilcoxon test for ordinal data

I would like to know if it is OK to use the Wilcoxon matched-pairs signed rank test to find significant differences between two sets of ordinal data, pre and post intervention (number of subjects is ...
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376 views

Select from Sign Test and Signed Rank Test based on assumption or power

I'm testing the difference of a paired dataset. I need to select between sign test and Wilcoxon signed rank test. I have read ...
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0answers
33 views

How to statistically compare two ordinal variables to find out the best one?

I have a dataset with two columns, each column representing a score of 1, 2, and 3. (Here is the Dataset) The ranks of first column is changed (or not changed) in the second column due to a process. ...
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3answers
804 views

Wilcoxon Signed Rank Symmetry Assumption

The assumption of symmetricity for signed rank test (and its relevance) is becoming extremely confusing for me. I am hypothesizing that sub-population A (before treatment) and sub-population B (after ...
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0answers
435 views

How to consider “pratt” zero method in Wilcoxon Test of R, which is available in Python Scipy?

I have a dataset of two columns which represent rank data. These ranks are ranged from 1, 2, and 3. To test the difference in medians between these two columns, I am considering the Wilcoxon rank-sum ...
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1answer
40 views

Wilcoxon ranksum test gives a p=0

I want to see if an app was effective in changing the behaviour of a group. Data were taken at baseline and after intervention on the same group. Since distribution doesn't follow normality I ...
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1answer
245 views

Help me understand the z-value computed in wilcoxsign_test (R, coin package)?

I'm using the coin-package in R to run comparisons on paired data using wilcoxsign_test. I use the exact version of the test, so I assume that the test goes through all permutations of the paired data ...
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1k views

Effect size for Wilcoxon signed rank test that incorporates the possible range of the attribute

I'm currently working on my master thesis and I'm analysing attributes obtained from digital elevation models (DEMs). I try to compare two point sets for which I extracted altitude values from two DEM ...
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weighted version of wilcox.test in R

I would like to compare my data to see if the means are different. The data is not normal so I am using a wilcox rank sum test to test for difference distributions. I would like to incorporate a ...