Mann Whitney U / Wilcoxon Rank-Sum Test in R | R Tutorial 4.3 | MarinStatsLectures October 21, 2019 30 By Stanley Isaacs CategoryArticles BlogTagsconfidence interval in r data science with r Mann whitney u test in r marin stats r marinstatlectures marinstatslectures non parametric test in r r programming for beginners tutorial r programming for data science r programming tutorial r statistics r studio tutorial R tutorial rstudio for beginners statistics for data science two sample t test definition two sample t test example two sample t test in r two sided t test Wilcoxon rank sum test in r 30 Comments Ageng Budiharjo Wijaya says: November 4, 2013 at 10:22 pm that is really helpful video. excellent! I was wondering how to use R studio for newbie like myself. Reply MarinStatsLectures- R Programming & Statistics says: November 4, 2013 at 11:34 pm Great to hear! We've got plenty of intro level R videos and are always producing more… Reply Shevtali says: May 4, 2014 at 6:28 pm Nice video, thank you! Reply Vanita Ramrakhiyani says: May 12, 2014 at 10:21 am Very nice..Thank you so much..it is quite educative video. Reply Haixiao Hu says: May 18, 2014 at 2:47 pm very clear and helpful! Reply Yasmine Karma says: June 10, 2014 at 1:49 pm Very useful tutorial. Straight forward, and emphasis on useful options and test statistics in R output. Reply Dev vasu says: August 1, 2014 at 10:21 am Very helpful Reply Laura Figueroa says: February 19, 2015 at 3:26 am Awesome, super clear! Reply Peibo Zhao says: October 26, 2015 at 7:19 pm Hello Mike, the video is pretty clear and easy to understand. I tried to use the same code to conduct the Mann-Whitney of my dataset in R studio. But it generated the error:"Error in wilcox.test.default(., RminTTC ~ as.numeric(Vehicle.pair), mu = 0, : 'x' must be numeric". I checked the class of those two variable and they are indeed numeric. So I have no idea how to solve this problem. Could you leave your email to me and help me? Thank you very much! Reply Emma Mah says: December 19, 2015 at 7:57 am Hi Mike, I'm trying to compare distance values of two groups but I get this error:Error in wilcox.test.formula(A ~ D, alt = "two.sided", exact = F, : grouping factor must have exactly 2 levels The two groups (A and B) have n=30 of different values. Reply Junhui Jiang says: January 2, 2016 at 12:01 am Hello, Mike. I have questions to ask you for help, if you are free.I am doing toxicity test. I want to compare control versus different treatment groups in a series tests, since I want to know if there are any significant differences.In one of my test:there are 5 individuals in an experiment unit, and 4 duplicates for each treatment. So totally there are 20 individuals. SO 5 individuals in the same experiment unit are integrated together in statistical analysis. Two variables in the comparisons: dose and incidence of malformation (sometimes this variable is mortality). I want to ask which type of test I should adopt: 1). if there is significant difference in incidence of malformation because of different doses; 2). if there is significant difference in incidence of malformation because of difference chemicals but same dose.Thanks a lot! Sorry to trouble you. Reply femaleforester says: January 28, 2016 at 6:13 pm Thank you for this very straightforward video. I want to use the Wilcoxon Rank Sum Test as a Post hoc test after Kruskal-Wallis-Test. I have 6 groups to compare. I found the command "pairwise.wilcox" for that, is that the Mann-Whitney-U-Test as well? Reply Josh Harvey says: March 25, 2016 at 4:52 pm Thanks so much for explaining this so clearly. I was wondering in the context of the video whether the numbers of either factor being tested within the set can effect the validity of the p value being produced. Specifically: does the fact that there are more non-smokers in the sample then smokers reduced the validity of rejecting the null-hypothesis? I'm working with a similar set of data (in that one factor I'm testing for has a higher frequency then the other) and was wondering if this is accounted for in the test. Reply Veadtuck93 says: April 24, 2016 at 9:28 pm Great video, very illustrative. Is there any non-parametric test that I could use to assess differences between two groups using an independent covariate? Reply Thyago Mendes says: November 4, 2016 at 9:19 pm Thanks! Reply yongling wong says: July 19, 2017 at 6:45 am Thanks for the clear explanation. May I know if I could still proceed with the test if there are some plots outside my boxplot which seems like outliers? Reply Evan Simpson says: January 9, 2018 at 3:14 am Fantastic video and incredibly straightforward. Question: How do you run the same test if you have a differing numbers of observations? For example, imagine I have four variables from seven locations each with a different number of observations. How would I conduct the test? Reply Oghenekome Dimaro-Eboreime says: March 30, 2018 at 5:52 pm Excellent! and straight forward Reply Candice Denner says: May 23, 2018 at 11:02 am Great video! I need to know what test to use in R when data is non-parametric but is ONE-SIDED. I tried this in R with the wilcox.test but an error is computed informing me that the argument must be two-sided. Thanks. Reply Nikki Kaplan says: July 26, 2018 at 7:14 pm Thanks for all the awesome videos! While I've followed all your tutorials to the T, I keep getting a very different w and p value after entering the wilcox.test command. Can you help me sort out what's going on please? It comes out looking like this: wilcox.test(LungCap ~ Smoke, mu=0, alt="two.sided", conf.int=T, conf.level=0.95, paired=F, exact=T, correct=T) Wilcoxon rank sum test data: LungCap by SmokeW = 1, p-value = 0.5714alternative hypothesis: true location shift is not equal to 071.42857 percent confidence interval: -5.325 1.000sample estimates:difference in location -3.775 Warning message:In wilcox.test.default(x = c(6.475, 9.55, 11.125, 4.8, 6.225, 4.95 : Requested conf.level not achievable Reply Ansh Sachdeva says: August 12, 2018 at 5:15 am what is 'mu' in the syntax and why is it taken to be zero? Reply P J says: October 4, 2018 at 5:25 am Thank you so much. Could you please teach about "how to apply a Wilcoxon test for ALL variables in columns at a time" (values of two groups are in the same column)? Reply Eric SOM DUTT says: December 21, 2018 at 11:11 am But how to check that they are not parametric Reply Nazia Pathan says: December 30, 2018 at 11:05 pm Hey. Thanks for the video! How does one correct for covariants, such as age, using Wilcoxon rank sum test? Reply Federico Mason says: January 7, 2019 at 9:51 am Thank you very much for the video. I have a question, can I study the interaction between two variables (let's say sex and age in your example) using the Wilcoxon Rank-Sum Test? Reply karthikeyan S says: February 28, 2019 at 6:38 pm Thanks for the wonderful explanation Reply MarinStatsLectures- R Programming & Statistics says: April 18, 2019 at 4:03 am 👋🏼 Hello there! In this R statistics video we learn to conduct the Wilcoxon Rank-Sum aka Mann-Whitney U test in R. This test is the non-parametric alternative to the independent t-test. Wilcoxon Rank-Sum (Mann-Whitney U) test is appropriate for examining the difference in medians for two independent populations. The LungCap R dataset that is used in this video is available here: (https://statslectures.com/r-scripts-datasets) ! If you like to support us, you can Donate (https://bit.ly/2CWxnP2), Share our Videos, Leave us a Comment and Give us a Like ! Either way We Thank You! Reply jinshi jian says: April 19, 2019 at 7:34 pm Hello, Mike, thank you for the video, it is great and useful to me. I have a question, I have samples from two group, but the observation is not equal (n1=40, and n2=150), one of that does not follow the normal distribution, can I use Wilcoxon test? If not, what should I use? Thank you very much. Reply Tien Trinh Nguyen Canh says: May 27, 2019 at 7:56 am Hi Marin, thanks for excellent and straightforward videos. I am now to R and I think that I meet the right page :). May I know if you have video on performing comparison of "more than two" nonparametric groups? I think it is equivalent to TukeyHSD test for parametric test. I could not find this video. Many thanks! Reply Poonam Bajaj says: May 28, 2019 at 5:15 am Can you make a video on how to find nth largest value of particular variable and print the whole Information about that particular case Reply Leave a Reply Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Save my name, email, and website in this browser for the next time I comment.