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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dependent T-test or Wilcoxons signed rank for small sample size?

I am doing an EEG study with a small sample size (N=13) and I have many variables that I need to compare (for example, onset of readiness potential, maximal point of RP, time or awareness, etc), so i ...
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22 views

Paired T test vs Wilcoxon signed-rank

I am trying to determine whether a paired T test or Wilcoxon ranked sum test is more appropriate to test for significance of improvement in the following: Patients were surveyed for pain scores ...
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1answer
17 views

Is it possible to compare 2 groups while controlling for something?

Is it possible to compare two groups (e.g., t-test, Wilcoxon, Mann-Whitney test, etc.) while controlling for something? E.g., I want to compare home ownership between military veterans and non-...
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13 views

How to test group differences when elements within a group are not independent?

I have 4 groups. Each group contains scores for items collected at different time stamps from a real-time system. Here is some dummy data: ...
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9 views

Cupcakes! Which Test for multiple Paired Data?

I have a cupcake factory. There are an infinite number of cupcake machines. We also have 5 taste testers. These taste testers claim to be in complete agreement over how they rate cupcakes. They claim ...
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19 views

Testing for significant differences between mutiple groups (some not normally distributed)

I have been trying to process data I collected in R, but not getting anywhere, so I hope someone can help me out. My question could be interesting for anyone who wants to compare more than 2 groups ...
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10 views

How to judge the result of Wilcoxon signed-rank?

I have used SPSS to perform Wilcoxon test. However I am somehow confused with two things. First of all, what does it mean when it said based on negative ranks?. ...
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1answer
59 views

Statistical test for random sample of data

I'm trying to determine if some particular measurements - in this case taken from a subset of genes of interest (50 genes) - show a significant difference to the rest of the population (15000 genes), ...
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1answer
36 views

Wilcoxon Signed Rank vs Bootstrapping for Skewed Cost Data

I'm currently looking at non parametric cost data (highly skewed to the right), and I'm trying to compare cost data pre and post intervention. Traditionally I've been taught that due to the non ...
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1answer
24 views

2 sample rank sum test

hi, the above question is one of the past exam question of the course which i am studying. The question i want to ask is: how can i answer part a)? I calculated the U=27 and mean = 15{(5*6)/2} , so i ...
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1answer
39 views

Why results from R's wilcox_test and Matlab's ranksum are not consistent?

I found when using two sample ranksum test, Matlab's ranksum gives different p value from R's wilcox_test (seems to be related to unequal sample size), I'm not capable of delving into their ...
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51 views

Prove the relationship between Walsh averages and Wilcoxon signed rank test

In my lecture notes it is stated that sum of all positive signed ranks (defined in Wilcoxon signed rank test) = the number of Walsh averages that are greater than median How can I prove this ...
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53 views

Significant two sided Wilcoxon rank sum test: Which group has higher median?

I conducted a Wilcoxon rank sum test with continuity correction, which produces W = 7195.5, p-value = 0.07094. This lets me confidently reject the null hypothesis of no true location shift at a ...
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94 views

How to report non-normal distribution and Wilcoxon in APA style

I have within-subject design and want to compare the means of two conditions. I first run the test for normal distribution and used Shapiro and p values are ...
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2answers
29 views

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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1answer
37 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
31 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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12 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 steps....
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54 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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27 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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22 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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13 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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1answer
25 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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33 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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33 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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84 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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18 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 cross-...
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34 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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25 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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116 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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36 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
67 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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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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24 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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14 views

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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115 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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1answer
55 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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1answer
55 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 $Z_i=\...
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1answer
24 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: https://gist....
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1answer
50 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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45 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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1answer
53 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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98 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 ...