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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Independent or Dependent Samples

I want to perform a statistical test: Wilcoxon Signed Rank Test to test if there is a significant difference between them, but I don't know if the two samples are dependent or not? Context: I have a ...
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33 views

Alternative to Wilcoxon signed-rank test with sample size < 6

I have to make a statistical analysis of only four (n=4) data pairs. I have tested two specific warm-ups for 4000m Team Pursuit in track cycling, and used a 250 m. sprint test as a meassurement of the ...
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1answer
19 views

Permutation test versus a Wilcoxon signed-rank test

I have data on arrival order for two individuals and I want to determine if one (y) is arriving consistently later than the other (x). ...
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9 views

statistical test in R for normalized time course data

gene time average stdev gene1 24h 1.1 0.01 gene1 48h 0.9 0.023 gene1 72h 0.7 0.01 gene1 96h 0.5 0.021 My data above ...
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5 views

How to take into account measurements of out-of-bound cases in a statistical pair-wise comparison?

I am doing simulations of different algorithms, and I compare them using the number of steps they need to reach their goal. To prevent the algorithms from running too long I put a maximum of 500 ...
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1answer
31 views

Why run a post hoc wilcoxon signed rank test after Friedman test, why not just skip to Wilcoxon sign test instead?

I understand that one is required to run post hoc tests after the Friedman test. For example, while the Friedman test may find a statistically significant change amongst 3 treatments, one may follow ...
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24 views

Comparison of two means when they are means of means?

I have two vectors "A" and "B". Each vector contains multiple mean values derived from observations. The two vectors are subsets of a sample that has been categorised into five vectors. All vectors ...
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19 views

determine which of the populations is “larger” with Wilcoxon/MannWhitney test

when using Wilcoxon test in Python - I get that one population is significantly different (greater) than the other. Where in the output do I get which population is actually the "larger" one? would ...
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8 views

Need verification of methodology for comparing two groups of sales data

I am looking for some methodology verification if anyone can help. I am looking at annual sales data for thousands of men (~12000) and women (~4000) using Stata 13. In the aggregate, women in this ...
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22 views

Should I use Wilcoxon Signed Rank or Mann Whitney U in this question?

Stats newbie here currently trying to teach myself some stats topics. When testing for evidence that mean earnings per share were higher in 1988, should I use Wilcoxon Signed Rank since the samples ...
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17 views

Effect size for Wilcoxon Rank Sum test

I'm unsure how to calculate the effect size after applying a Wilcoxon rank-sum test. I'm using scipy.stats.ranksums, where the outputs are ...
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28 views

How do I check data for normality, then what next…?

I am currently undertaking a hypothesis test for some financial returns data. I'm getting slightly confused on parametric versus non-parametric testing. I am testing a market portfolio of 305 stocks ...
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80 views

Wilcoxon Signed Rank Critical Values for n >40

I'm looking for critical values for Wilcoxon Signed Rank for larger values of N but can only find tables and lists for up to N=40. I am looking for either comprehensive sources of critical values for ...
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11 views

Wilcoxon signed rank test [duplicate]

I am investigating attitudes towards different types of disabilities disabilities. I expect physical overall to be recognised more compare to mental and intellectual. All of my results are significant ...
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11 views

SPSS Friedman post-hoc - determining best classifier

I'm a newbie, so sorry if the question is too straight forward. I'm comparing 5 algorithms on 10 different data sets. In SPSS I did a Friedman test, and the null hypothesis is rejected. Now I would ...
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21 views

Compute test-score statistical significance using control-scores from shuffled population

I am not a statistician therefore need your help in computing statistical significance of my data. Suppose I have 2 baskets (B1 and B2) on a table each with mix of apple and oranges, and there are 10 ...
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15 views

(Repeated) Cross-Validation and Wilcoxon test

Is it a common practice to apply the Wilcoxon test to the (repeated) cross-validation score estimates when comparing two different models? I've read that most of the time the average of the ...
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27 views

Is the Wilcoxon Rank-sum test the best option with many near 0 values >0?

I have a two very large datasets. They look something like this, but with a few thousand rows. They are the total number of tyrosines in a short DNA sequence with a length of up to 5. A would precede ...
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23 views

Understanding the Wilcoxon rank-sum one-sided test

With a simple two sided test, the null hypothesis is often set as: Hn: µ1- µ2 = 0 and if we get a p-value less than 0.05, we can reject the null hypothesis and accept the alternative. That is: ...
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102 views

Looking for the right statistical test. - Wilcoxon signed-rank test?

I'd like to test if three data sets are statistically similar, but I'm not sure which test is the right one (because the examples on the internet are all very simple). I start with a list of values (1 ...
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26 views

Is it possible to compare unequal sample sizes in a non-parametric paired t-test?

I'm trying to compare counts of species made during the day and during the night. The counts were made in the same location for day and night and were on the same populations. Therefore, I'm assuming ...
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23 views

Test for Divergence in Two Large Vectors Non-Normally Distributed

I have very large sets of biological data, ca. 5,000,000 points, which are the proportion of methylation throughout the genome. Data is therefore on 0-1 scale. I am looking at testing distribution ...
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1answer
51 views

How to compute difference in location computed in Mann-Whitney-test?

I would like to reproduce the results of the Wilcoxon-Mann-Whitney-test in R wilcox.test(x,y,paired=FALSE, conf.int=TRUE. I succeed to get the W-value but didn't ...
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10 views

How to compare the change (increase or decrease) for two pairs using one-way Wilcoxon signed-rank test?

Suppose I have $X_{before}$, $X_{after}$ and $Y_{before}$, $Y_{after}$ (before and after the drug). Each variable have 15 observation, i.e 60 in total. I used one-way Wilcoxon signed-rank test to see ...
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17 views

Wilcoxon rank test where sample sizes are very different

I am undertaking a Wilcoxon rank test between two samples - say A and B. The number of observations in B is about 10 times the number of observations in A (1000 vs 100). Does this discrepancy in ...
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22 views

Can the Mann-Whitney U test be used for related data?

I am comparing the annual profit margins of a set of 15 restaurants before and after they gained a "Michelin Star". I have multiple non-uniform numbers of profit margins for each restaurant before ...
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27 views

How to Collapse Correlated Data for Wilcoxon Signed Rank Test and Sign Test Such that the Power Loss is Minimum?

Data Description: I am trying to evaluate my algorithm against 1 benchmark and 3 other algorithms (so, 5 total algorithms). I collected some data using the following procedure: I feed 10 iid ...
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Non-normal, related but non-paired data, test for significant difference

i am comparing the profit margins for restaurants prior and post gaining a michelin star. I have all the profit margins for each restaurant up to 2-5 years prior and post. I want to compare all of ...
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101 views

Paired t-test vs Wilcoxon signed rank

I conducted a pilot study (n=14) which was evaluated retrospectively. I have four parameters with a pre-intervention and post-intervention score that I want to compare. I am wondering whether I can do ...
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40 views

Rules for Percentage of zeros in a zero inflated model

What percentage of zeros in the data should make us consider trying the sequence of models: Poisson -> Negative Binomial -> Zinf-Poisson -> Zinf-Negative Binomial, etc? I have two datasets with about ...
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53 views

Central Limit Theorem for Wilcoxon signed rank tests

Let $X_i, i=1,2,...,n$ be a set of iid observations, assumed symmetric about $\mu$. Let $R_i$ be the rank of the absolute deviations from some $\mu_0$, i.e. $R_i=\text{rank}(|X_i-\mu_0|)$. Let ...
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1answer
21 views

Problem with Wilcoxon test in SPSS

I have a question about Wilcoxon test in SPSS. For a work in my university i have to test 2 results of metrics applied in 2 algorithm (A2-NSGA3 and NSGA2), the results are as follows: ...
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41 views

Finding direction of inequality for two-tailed test

I'm comparing two sets of measurements using a paired difference test (specifically the Wilcoxon signed-rank test). I would like to find out whether there is a significant difference between these ...
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44 views

Hierarchical Wilcoxon signed-rank test?

I have a small number (<10) surveys given to a small number of respondents (<10) before and after a program of instruction. The survey responses are on a Likert scale, and the results of all ...
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35 views

Comparing Two Cohorts, Pre and Post scores

I'm working on a research project, and I could use a little assistance in picking the correct test. There are two cohorts that took a pre-test. Subsequently, the intervention group was given a ...
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70 views

Non-parametric repeated measures with replicates: Wilcoxon Rank Sum Test or Wilcoxon Signed Rank Test?

We want to assess the suitability of 2 devices A and B for performing a test task on a set of subjects. We use a quantitative measure to evaluate performance (i.e., time to complete the task). We are ...
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9 views

Should I rely on the result of Wilcoxon Signed rank or Kruskal Wallis?

I am writing a dissertation on the relationship between age but also investigating other factors such as income, and pro-environmental behaviour. If i test household income against 'Have you taken ...
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2answers
59 views

Positive average but negative z-value (Wilcoxon Signed rank test) [closed]

Can anyone explain why I get a negative z-value when I perform a Wilcoxon test but my average is positive?
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1answer
27 views

Wilcoxon Signed-Rank Test for one population

It seems that Wilcoxon Signed-Rank Test could be used not only for inference about the mean difference in a matched pairs, but can also be used for one sample setting. Now I have a dataset which is ...
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8 views

wilcoxon sum rank test steps when variables are measured in group

how to perform Wilcoxon sum rank test when one want to measure 3 variables and each variable data is to be collected from at least 6-7 questions. There are two sets of data of before and after ...
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31 views

Testing of pre-post differences for multiple conditions and non-normal distributed data

I have pre- and post-test behavioral data (response times) of 9 people (1 group). The task which people performed was divided into 5 sections which differed in the stimulus type. So I have variables: ...
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24 views

How can I control for a variable while conducting Wilcoxon Rank Sum Test?

I did a Wilcoxon rank sum test to figure out if there is any difference in the distribution of Variable X1 for two groups. The test results showed that the difference does exist. I, however, suspect ...
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2answers
49 views

How to apply Wilcoxon test to small sample with NAs?

I have the following data which show some values before and after a drug. I want to test whether the drug increased the mean. I think I should use Wilcoxon test, but I don't know what to do with ...
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1answer
181 views

How to choose between sign test and Wilcoxon signed-rank test?

I am trying to pick one from these two tests to analyze paired data. Does anyone know any rules of thumb about which one to pick in general?
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23 views

multiple comparison for discrete nonparametric distributions

I have N=24 controls and M=10 patients. (M can be 20 later) Each subject has one 3D image, each element of the image is a discrete value (integer) ranging from 0 to 4 [0,1,2,3,4]. It's like a score. ...
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28 views

calculating tabulated interval for Wilcoxon-Mann-Whitney rank sum test using R

I am following along with two tutorials on R-bloggers (both utilize the stats package). The first is for the Wilcoxon signed rank test (http://www.r-bloggers.com/wilcoxon-signed-rank-test/) and I am ...
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1answer
42 views

Unequal Sample Size and Wilcoxon Rank Sum Test

It is my understanding that it is okay to perform the Wilcoxon Rank Sum test with slightly unequal sample sizes. I just don't understand how the Wilcoxon accounts for the missing numbers in one group ...
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824 views

Have the reports of the death of the t-test been greatly exaggerated?

Reading through CV all-time classics I came across a statement that I would like to clarify. This is the post and my question refers to the closing remarks: "I have to note that all of the knowledge I ...
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78 views

Difference in mean between two periods in a time serie? What test to use?

I have a dataset of multiple experiments measured each hour, for 56 hours. Now I want to identify if there is a significant difference in the mean value between the time periods 1-2 hour and 50-57 ...
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56 views

multiple comparisons correction

Let's say I have the done the following biological experiment: I have 10 genetically different bacterial clones, which I have competed against a common reference clone (ancestral). I can then ...