Frank Wilcoxon, chemist and statistician, best known for the Wilcoxon-Mann-Whitney (rank sum) test and the Wilcoxon signed-rank test, two widely used nonparametric rank-based tests.

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33 views

Two groups are significantly different? Test to use

I have two groups of discrete data (integers): ...
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18 views

Wilcoxon Signed Rank when subjects appear in each sample n times.

I have sales data and would like to see if the median sales for an employee has increased as a result of this training. Thus, I have pre and post data, since it is only six months and am interested in ...
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31 views

Wilcoxon matched pair signed rank test after using CEM

Can I run a Wilcoxon matched pair signed rank test after using Coarsened Exact Matching to match data? If yes, please guide me through the process. I use STATA.
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37 views

Can I use wilcoxon signed rank test for time series data

I have a question about wilcoxon signed rank test. I have 2 different speed profiles (speed starts from time 0 to 100 sec) of the same participant that was given 2 different treatment. I would like to ...
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12 views

Comparing patient proportions between one ER and the national average

I am looking to compare the proportion of emergency room attendances by hour of the day against a national average proportion (plus some other tests for ER variables such as referral methods and ...
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0answers
15 views

testing for differences in means after an experimental change

I have a set of Mechanical Turk-like workers who have been paid $0.25 per task to complete tasks from a finite, but very large, pool of tasks, and I have data on how many tasks they've completed and ...
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1answer
75 views

Performance Evaluation for multiple classifiers in machine learning with Wilcoxon Rank Sum Test

I use four feature descriptors for five independent runs with each run randomly selecting the training set and testing set from the total labeled samples. SVM is the classifier. After acquiring the ...
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2answers
47 views

How to test for significance if the variances are different?

If got data (value) of two types (cond true or false): ...
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1answer
34 views
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3answers
149 views

Testing if two non-normal distributions are significantly different (K-S or Wilcoxon or both?)

The Big Question I'm trying to decide between K-S and Wilcoxon (or something I haven't thought of yet) for two data sets I want to prove are significantly/insignificantly different from one another ...
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49 views

analysis of non-normal data

I collected some data on a species of goose called Brent Goose over the winter. A csv file of the data can be downloaded from Dropbox or imported straight into R with this code: ...
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24 views

How to interpret results from a nonparametric Wilcoxon test [duplicate]

I did a research study that looked at pre and post test scores from a test. I was asked to run a Wilcoxon test, which I did and now I need to know how to interpret the test results but also how to ...
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1answer
53 views

Paired or unpaired Wilcoxon test?

I counted the number of geese on an intertidal mudflat on 100+ days over the winter. I made two counts on each of these days: one at low tide and one at high tide. I want to know if the number of ...
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1answer
114 views

Non parametric Wilcoxon Signed Rank test

I have the following data vector(in fact its 2392 data points long): ...
2
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1answer
78 views

Wilcoxon rank sum test methodology

I'm comparing the performance of two algorihtms $A$ and $B$ based on a metric. For each algorithm, I have $31$ independent samples that represent its performance. This samples are grouped in two ...
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70 views

Is pairwise wilcoxon test a valid non-parametric alternative to Tukey's HSD test?

I am trying to identify significant differences between groups from normal and non-normal distributions. When the distribution is normal the workflow is pretty straightforward: ANOVA and after that a ...
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1answer
33 views

Why do we assign fractional ranks in rank tests?

Both Mann-Whitney U test and Wilcoxon signed rank test follow this procedure: sort the data assign ranks, Ties receive a rank equal to the average of the ranks they span compute the statistic using ...
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1answer
18 views

Distribution heavily stacked on either limit - appropriate test?

I have two sets of results from an experiment that produces distributions with extremely heavily stacked sides and mostly uniform elsewhere. The aim of my analysis is to answer a the question roughly ...
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1answer
469 views

Difference between the Wilcoxon Rank Sum Test and the Wilcoxon Signed Rank Test using paired observations

I was wondering what the theoretical difference is between the Wilcoxon Rank-Sum Test and the Wilcoxon Signed-Rank Test using paired observations. I know that the Wilcoxon Rank-Sum Test allows for ...
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0answers
89 views

Bonferroni correction for two different tests on the same dataset

I am having trouble figuring out the correction factor to choose for a Bonferroni correction. Let me explain. I have two datasets, control ($x$) and data from left ($y_1$, affected limb) and right ...
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1answer
52 views

Adjustment of medians in the Siegel-Tukey test vs. the Wilcoxon test

I have two (unpaired) distributions. The distributions are far from being normal, so I'm using the Wilcoxon test to compare their medians: the Wilcoxon test does not reject the null-hypothesis ...
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1answer
49 views

Wilcoxon test to support logistic regression

I want to test the hypothesis that IV 2 (post-test value) is a better predictor for the criteria (no success vs. success) than IV 1 (pre-test value). Those IVs are indicators for static vs. dynamic ...
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1answer
33 views

what kind of non-parametric test to use?

I collected data on one sample, the DV could be separated into two groups (success yes vs. no) and then I have several IVs with interval scale. I just don't know if to use Wilcoxon or Man-Whitney ...
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2answers
136 views

Skewness adjusted t-stat

I've some data that is divided into a series of groups and am testing whether the mean is different from 1. The data is highly skewed, with skewness ranging from 1.10 to 26! I did a one-sample t-test ...
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19 views

Measuring treatment effect on top-ranked subjects selected at point in time from longitudinal data

I am trying to measure the effect of treatment after some time on a group of subjects who were selected for treatment because they were the highest (top 1200) ranked subjects during a single period ...
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1answer
109 views

Use of Wilcoxon test for non-normal data akin to Two One Sided T-test

I'm analysing paired data for equivalency and it's not normally distributed, i.e., the difference of the paired result is not normally distributed due to, amongst other things, outliers. If it were ...
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2answers
85 views

Testing which groups have had a significant change

I have three groups with two hundred individuals each, and each individual within a group has a pre and post treatment measurement. A single group contains individuals with similar pre measurement ...
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1answer
226 views

Applying a post hoc Wilcoxon signed rank test to a Friedman when there are different sample sizes

I conducted a Friedman test to related-sample group in three conditions (pre-treatment, post-treatment and 6-month post treatment). Out of 216 participants that completed the first two stages, 50 of ...
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38 views

List of sample arrangements at a given Wilcoxon / Mann-Whitney test statistic

Consider a Wilcoxon-Mann-Whitney test statistic, either in the form (i) "W = sum of ranks in sample A"; or in the form (ii) "sum of ranks in sample A - the minimum possible sum of ranks in sample ...
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2answers
202 views

Is the W statistic outputted by wilcox.test() in R the same as the U statistic?

I've recently been reading about the Mann-Whitney U test. It turns out that to carry out this test in R you actually need to run a Wilcoxon test! My question: is the W statistic outputted by ...
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1answer
134 views

Can I use Wilcoxon Signed-Rank Test to test pairs of data in a time series?

I have a dataset of measurements (non-normally distributed). Each line of this dataset is composed by two measurements of the same variable in a specific time (i.e. XYY [time, meas1, meas2]). This ...
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1answer
219 views

Wilcoxon one-tailed test

It's regarding a one-tailed Wilcoxon sign test. I am comparing (fictional) ratings of liking before and after a woman shaves off the hair. The design is complicated. I will do my best to explain. ...
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2answers
280 views

Should I expect a Z-Score as an output from a Signed Rank test?

I have some data that is highly skewed. I want to test whether the median of the data is different from 1, so I decided to use a Wilcoxon Signed Rank test. The description and implementation of this ...
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0answers
39 views

Which test should I run?

I have RNA sequencing data (= expression of a certain protein) from the lung tumor of 14 patients, 5 non-smokers and 9 smokers. If I want to compare the expression level of that protein of smokers vs ...
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1answer
1k views

Large difference between Mann-Whitney test and Wilcoxon signed rank test significance

I am looking at a success of textual requests. We have a dataset of matched pairs, one successful, one not successful, and they are matched based on length of the request in words (since I want to ...
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1answer
179 views

Wilcoxon signed rank test on anonymous sample

I carried out a test on a group of 100 people. The test contained 10 questions with 5-point Likert scale answers (1 = Strongly Agree, 5 = Strongly Disagree). After the test was conducted, the group ...
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2answers
341 views

How to best visualize one-sample test?

We are currently writing a paper with several one-sample Wilcoxon tests. While visualizing two-sample tests is easy via boxplots, I was wondering whether there is any good way to visualize one-sample ...
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3answers
901 views

Paired t-test for binary data

I have one sample with n=170 and two binary variables (A,B) that can take as a value 1 or 0, where 1 counts as a success and 0 counts as a failure. What I want to know is whether the means of these ...
2
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1answer
110 views

Why do zero differences not enter computation in the Wilcoxon signed ranked test?

The Wilcoxon signed ranked test tells us if the median difference between paired data can be zero. The test is executed by computing a statistic, then a z-score and comparing it to a critical value. ...
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0answers
83 views

Nonparametric test for trend using Python

I am looking to perform a nonparametric test for trend on a continuous outcome across three groups, preferably in Python. For example height (pretend height is not normal) in 4th, 5th and 6th ...
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1answer
146 views

How to set confidence level for wilcoxsign_test (package coin)?

In R, the function wilcox.test takes the argument conf.level = 0.095 (for example). Giving the same argument to the function ...
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1answer
84 views

Test to rank methods by AUCs on various benchmarks

Suppose I have N methods and M benchmarks. I have an AUC statistic (and some other similar statistics) for each combination of method with benchmark. What test should I use to test if one method is ...
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0answers
44 views

Which of these two ways is better to report comparison of paired data?

Suppose I am comparing the computational time of two algorithms A and B. They are solving randomized problem P. Let's say I solved the problem for seeds $ 1, 2, \dots, n $ with both A and B and got ...
5
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1answer
334 views

Relative efficiency of Wilcoxon signed rank in small samples

I have seen in published literature (and posted on here) that the asymptotic relative efficiency of the Wilcoxon signed rank test is at least 0.864 when compared to the t test. I have also heard that ...
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53 views

Is Wilcoxon Signed Rank my solution?

A) I have: a pre and post measurement on 7 ordinal/scale variables for every participant (=student in classroom) 1 intervention 5 classrooms of students 3 teachers implementing the intervention I ...
14
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3answers
404 views

Repeated measures over time with small $n$

I was given data to analyze for a study looking at the effects of a treatment on iron levels at four different time points (before treatment, the day treatment ended, 4 weeks after treatment, and 2-4 ...
3
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4answers
949 views

Testing for significance between means, having one normal distributed sample and one non normal distributed

I have following problem: Within an independent groups 1-factor design I have two independent groups, with a sample size of 20 each. The data of the treatment group is not normally distributed, ...
3
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1answer
92 views

Alternative to Wilcoxon signed-rank test, for data where many pairs are equal

I have several discrete datasets with a small range (-2 to +2) which I want to test against the null hypothesis "the distribution is centred around zero". The Wilcoxon signed-rank test was suggested ...
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2answers
75 views

Can I compare the p-values of two Wilcoxon tests?

I am comparing three distributions of values. Let's say A, B and C. If I find that the p-value of the Wilcoxon rank sum test between A and B is 1e-08 and between A and C is 1e-10, can I say that ...
5
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1answer
154 views

Evaluating software performance to identify regressions resulting from source code changes

I am attempting to monitor the performance of a software package in order to identify when a change to the code base introduces a performance regression (a slow down in the code). My assumption is ...