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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wilcox.test usage in R

I would like to know if there is a difference in the values taken from measurements of a given characteristic sampled at primary forest (Point=1) and secondary ...
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26 views

Confused about the proper way of testing for an improvement or worsening

I want to check if a new equipment improves a score compared with the older equipment. My database contains the score with the old equipment, and the scores with each new equipment. I googled, ...
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16 views

Rank Order Analysis with Missing Values

I have several survey questions that allow a respondent to choose their top three choices from a set of potential answers--basically "What is the most important, 2nd most important, 3rd most ...
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2answers
117 views

Why am I getting inconsistent results from Wilcoxon signed rank test and Kruskal-Wallis test?

I am doing a study on 3 drugs, comparing response pre-post treatment. My objective is to know if these drugs are effective and which one is better. I used non parametric tests since the results ...
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1answer
23 views

Wilcoxon tests in Doronix Math Toolbox

I'm using Doronix Math Toolbox. They have statistical functions (http://www.doronix.com/statistics.html). I can't figure out how they are finding p-value in ranksum and signsum tests. Does anyone know ...
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4answers
42 views

Two groups are significantly different? Test to use

I have two groups of discrete data (integers): ...
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19 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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38 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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52 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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16 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
80 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
52 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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38 views
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197 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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52 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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25 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
60 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
129 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
84 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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81 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
38 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
733 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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104 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
61 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
54 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
35 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
151 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
119 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
86 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
249 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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41 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
238 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
149 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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263 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
319 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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41 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
2k 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 ...
2
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1answer
191 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
354 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
1k 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 ...
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1answer
116 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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90 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
153 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
90 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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46 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 ...
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1answer
364 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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54 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 ...