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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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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
30 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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18 views

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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17 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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18 views

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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37 views

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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27 views

Comparing groups? Wilcoxon, Paired test?

I am carrying out a simulation experiment where a fixed number of resources are, at the end of the simulation, divided between two groups of individuals, 'A' and 'B'. There may or may not be the same ...
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1answer
97 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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39 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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37 views

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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32 views

What are the implications of asymmetry in the Wilcoxon signed-rank test?

I have samples $a$ and $b$ from pre and post treatment conditions on same participants. The empirical distributions of both these samples are skewed positively. The paired differences $a_i-b_i$ do not ...
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1answer
219 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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2answers
107 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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1answer
146 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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2answers
207 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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28 views

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
64 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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2answers
206 views

Scipy Wilcoxon test: rejection direction

One-sided test Lets say I want to compute one-sided wilcoxon test: R: ...
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734 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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1answer
62 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
91 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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26 views

Wilcoxon missing

I want to do an analysis of data related to the Wilcoxon test, there are 150 data; The problem is that prior to the intervention I have around 10% of lost values, in the comparator I have them ...
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229 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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29 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
367 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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299 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
25 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
99 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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3answers
796 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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67 views

Compare ranks between sets of rankings

I have a set of ~1300 genes ranked ordinally for 6 experiments (2 treatments with 3 replicates each). That is I have six sets of rankings from 1 to 1300. The replicates are not necessarily identical ...
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104 views

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 ...
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426 views

One-tailed Wilcoxon signed-rank test

I have a dataset of paired observations (let's denote X before the treatment and Y after), and I want to test if the distributions are significantly different. Here, I think that a wilcoxon signed-...
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2answers
55 views

Not sure if my data fits using a Wilcoxon Signed-rank paired test

I have count data measuring the wildlife (animals) crossing a passage. A modification was made to the connecting passage. I want to measure whether this affected the rate of wildlife crossings. The ...
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38 views

Statistical method comparing difference in extreme percentile

Statistical methods like wilcox.test to t.test test differences in medians or means. I would like to compare the difference in ...
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33 views

single p value from multiple experiments using the Wilcoxon sign rank test

Suppose I perform five identical independent experiments. Each experiment compared values between pairs of the same matched samples. Does it make statistical sense to compute a single p value from ...
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48 views

Calculation of the estimate for probability of a positive Walsh average in a Wilcoxon Test

Is the estimate for the probability of a positive Walsh average is just the number of positive Walsh averages divided by the number of Walsh averages? In other words, can be infer the distribution of ...
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1answer
236 views

Bonferroni correction for Wilcoxon signed rank test with 6 related samples?

I am comparing scores of the same group of people over 7 days. I first did a Friedman's test to know where the differences were between the 7 days and I did a Wilcoxon signed rank test for the Post ...
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Comparing a traditional and technology based tool

I am trying to compare a printed word dictionary with a digital dictionary that included added features like sound and video feedback. For this I have selected 60 participants and asked 5 questions (...
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2k views

How to deal with ties in Wilcoxon Signed-Rank Test

I'm using a Wilcoxon signed-rank test to compare two related samples of non-normally-distributed data. The data contains some ties, so when I run the test in R, I get this warning: ...
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595 views

Symmetry assumption in Wilcoxon's Signed Rank Test

I'm trying to understand the assumptions in Wilcoxon's Signed Rank Test. From here I understand that "The test is based on signed-rank of observations that are drawn from a symmetric continuous ...
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13 views

Why are all possible sets of Wilcoxon ranks equiprobable?

Consider a sample of size $n=3$. The sample is assumed to come from a distribution which is symmetrical about a median $M$. The absolute differences of the values of the sample are calculated and ...
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51 views

How to use Wilcoxon on comparing Likert items with different numbers of options

I really need urgent help on this issue. I want to use Wilcoxon Signed-rank test to compare two Likert items, the first is being 9 point and the second one is 4 point Likert. Moreover, in the first ...
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1answer
102 views

Over- or underestimation of Wilcoxon Rank Sum Test and Wilcoxon Signed Rank test?

I have noted the differences between the tests, as answered here (Difference between the Wilcoxon Rank Sum Test and the Wilcoxon Signed Rank Test). However, I would like to know whether there are ...
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122 views

What conditions of normality must be met for paired/unpaired t-tests?

We assume that $X_i \sim N(μ_1, σ_1^2)$ and $Y_i \sim N(μ_2, σ_2^2)$ [i.e. that they are normal distributions with a finite (or known?) mean and variance] [...] -- Tamhane & Dunlop, ...
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1answer
55 views

Comparing three softwares

As part of my research I have developed a software and I wanted to test it with 2 other softwares that does similar work. The problem is I could find only few users of these two softwares (20 users ...
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1answer
93 views

How to carry out the Wilcoxon test to compare multiple classifiers?

I have run some unsupervised domain adaptation algorithms on two data sets. (TJM, JDA, GFK, and ARTL). I read this paper that states that the Wilcoxon test is better than parametric tests. I am trying ...
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150 views

Calculate sample size for one-sample Wilcoxon test

My question builds up on following post: Sample size calculation Wilcoxon rank-sum test The user asks how to calculate the statistical power of a Wilcoxon rank-sum test. Benjamin comes up with a ...
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0answers
18 views

test to know if two observations at different times comes from the same distribution

I am working on a performing of a Linear Discriminant Analysis, the provided dataset is given in the following way: Is observed 4 times a syringe of a medicine, each observation in different times ...
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7 views

Question about testing one variable measured in different times

I have the next problem, I have a dataset of a experimental measures of a variable $X_1$ It has been measured at time $t_1$, then the same measure of the has been measured at $t_2$, getting $X_2$. For ...