# Questions tagged [wilcoxon-signed-rank]

a non-parametric rank test to compare two paired samples, whether values in one are bigger than in the other. This test is NOT the same as the sign test.

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### Effect size to Wilcoxon signed rank test?

Some authors (e.g. Pallant, 2007, p. 225; see image below) suggest to calculate the effect size for a Wilcoxon signed rank test by dividing the test statistic by the square root of the number of ... 5k views

### Why is the asymptotic relative efficiency of the Wilcoxon test $3/\pi$ compared to Student's t-test for normally distributed data?

It is well-known that the asymptotic relative efficiency (ARE) of the Wilcoxon signed rank test is $\frac{3}{\pi} \approx 0.955$ compared to Student's t-test, if the data are drawn from a normally ...
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### 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 ...
27k views

### Wilcoxon rank sum test in R

I have results from the same test applied to two independent samples: ... 4k 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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### 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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### 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 of two measurements of the same variable at a specific time (i.e. XYY [time, meas1, meas2]). This ...
18k views

### Non-parametric test if two samples are drawn from the same distribution

I would like to test the hypothesis that two samples are drawn from the same population, without making any assumptions about the distributions of the samples or the population. How should I do this? ...
68k views

### What is the difference between the Wilcoxon Rank Sum Test and the Wilcoxon Signed Rank Test?

What is the difference between the Wilcoxon Rank-Sum Test and the Wilcoxon Signed-Rank Test using paired observations? I know that the Rank-Sum test allows for a different number of observations in ...
10k views

### Is ordinal or interval data required for the Wilcoxon signed rank test?

Having looked at multiple online sources, I can't seem to get a straight answer. Could someone please clarify for me if ordinal data is sufficient to use for the WSRT and if not, is the sign test an ...
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### Output of one-tailed Wilcoxon sign rank test in R

I'm trying to assess the difference between two algorithms. They are stochastic, so I've run them multiple times against the same input files and noted their results. I want to determine whether my ...
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### 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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### 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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### How is the confidence interval built when executing the Wilcoxon.test in R?

I want to calculate the confidence interval around the median obtained from this data set: ...
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### What method is preferred, a bootstrapping test or a nonparametric rank-based test?

I want to perform a single-tail test on a single sample of real numbers (N~100) against an expected value. The population is known to be not normally distributed. So from what I've read about stats, I ...
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### 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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### 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 ...
2k 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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### 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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### 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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### wilcoxon signed rank test to test paired data?

I want to test whether the difference between the pairs of students's scores follows a symmetric distribution around zero.See below ...
2k views

### Is Wilcoxon Signed-Rank Test the right test to use?

I have a dataset of the following form: ...
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### 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 ...
5k views

### Wilcoxon signed-rank test for proportion variable response?

My response variable is a proportion. The explanatory variable is categorical with two levels which are not independent. The distribution of the response variable is different from normal. ...
1 vote
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### How do you calculate the effect size of one-sample Wilcoxon signed-rank test?

Can you / how do you calculate the effect of a one-sample Wilcoxon signed-rank test? Is there a way to perform the calculation in SPSS or another software package?
617 views

### Pseudo median from Wilcoxon signed rank test larger than sample median?

I am left wondering, why I can be in a situation where the pseudo median (population estimator) of a Wilcoxon signed rank test, can be larger than the simple differences between sample medians? I am ...
2k views

### In what situation would Wilcoxon's Signed-Rank Test be preferable to either t-Test or Sign Test?

After some discussion (below), I now have a clearer picture of a focused question, so here is a revised question, though some of the comments might now seem unconnected with the original question. It ...
29k 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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### Alternative to the Wilcoxon test when the distribution isn't continuous?

One of the assumptions for using the Wilcoxon sign-rank test is that the underlying distribution is continuous (see here.) However, there are cases (for example, when analyzing Likert scale data) ...
7k 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. ...
439 views

### If the difference of scores is normally distributed, the sample distributions don't matter in a paired t-test, right?

I have a very straight-forward question: If the difference of scores is normally distributed, the sample distributions don't matter in a paired t-test, right? Therefore, If the samples are not ...
32k 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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### Paired t-test with multiple observations per pair

I have a bunch of websites websiteA....websiteZ for example. Now I have an optimization technique that possibly improves the performance of these websites. I want to check whether this technique ...
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### What differentiates the wilcoxon test from t test regarding ordinal variables?

I'm wondering what the wilcoxon test differentiates from the t test so it can be used with ordinal variables. In other words why can't we use a t test for ordinal variables but can we use a wilcoxon ...
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### Same p-value. Is it normal?

I did the following comparisons with a Wilcoxon test on MatLab, and I got the same p-value on both. Is this normal? Is there something wrong? Also, the tests indicate not to reject H0. How to ...
2k views

### Appropriate visualization for the Wilcoxon signed rank test

I have question regarding the Wilcoxon test and if the results can be represented visually. I had 10 participants in my experiment where by I asked participants to read sentences and then they ...
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### Exactly what does the Wilcoxon signed rank test compare?

The Wilcoxon signed rank test is a nonparametric version of the t-test. That is, it converts parametric values, which may be non-normally distributed into EDIT for Glen_B more normally distributed ...
2k 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 ...
2k views

### How to interprete and describe the results of a Wilcoxon Signed Rank test?

I'm trying to learn about rank tests, and having doubts abouut how I should a result from a Wilcoxon Signed Rank test. Suppose, we are given: Z = -2.201, r = - 0.845, P < 0.05, then how should I ...
454 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 ...
10k 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 ...
282 views

### Is my interpretation for Wilcoxon Signed Rank test correct?

I ran a wilcoxon signed rank test on paired samples where the outcome variable was a test score. The samples were paired by as siblings (younger and older sibling). I have a problem interpreting the ...
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### Calculating statistical power for non-parametric data (using Wilcoxon signed-rank tests)

I am performing a prospective-design analysis of Patient Reported Outcome Measures from a registry of patients. I have used Shapiro-Wilk test throughout to test for normality. All data is paired and ...