Kruskal-Wallis test

Click here for free Online Virus Check from Panda Antivirus

Google

Web This Site

Featured Article: Where to start...

Documents for quality control plans, internal audit plans, ISO 9001, ISO 9001:2000, management systems, mil-i-45208, QC manuals, quality control manuals, quality control systems, quality management systems, total quality management

Get Adobe
 
Construction
Manuals
Procedures
FAA
Forms
Kits
ISO
Gov

Helpful Links
 
Basics
Copyright
Link Directory
Link Exchange
Privacy
Resources
SPC Definitions
Stat Guide
Where-to-Start

Non-Tech Links
 
Cool Tool
Frustration
Inspiration
Opinion
Nonsense
Serious


Sponsored Links
 

 

Kruskal-Wallis test


The Kruskal-Wallis test is used to test the null hypothesis that multiple population distribution functions (corresponding to multiple samples) are identical against the alternative hypothesis that they differ by location.

(For two samples, the Kruskal-Wallis test is equivalent to the two-sample rank-sum test.)

Assumptions:

  • Within each sample, the values are independent, and identically distributed. (The Kruskal-Wallis test is a nonparametric test. We need not specify or know what the distribution is, only that all the values in each sample follow the same continuous distribution.)
  • The samples are independent of each other.
  • The populations from which the different samples were taken differ only in location. That is, the populations may differ in their means or medians, but not in their dispersions or distributional shape (such as skewness).
  • For multiple comparisons to be meaningful, the treatment effect is viewed as fixed, so that the populations (treatment groups) in the experiment include all those of interest.
  • Because the test statistic for the Kruskal-Wallis test is based only on the ranks of the data values, the test can be performed when the only data available are those relative ranks.

Guidance:

  • Ways to detect before performing the Kruskal-Wallis test whether your data violate any assumptions.
  • Ways to examine Kruskal-Wallis test results to detect assumption violations.
  • Possible alternatives if your data or Kruskal-Wallis test results indicate assumption violations.

To properly analyze and interpret results of the Kruskal-Wallis test, you should be familiar with the following terms and concepts:

If you are not familiar with these terms and concepts, you are advised to consult with a statistician. Failure to understand and properly apply the Kruskal-Wallis test may result in drawing erroneous conclusions from your data. Additionally, you may want to consult the following references:
  • Brownlee, K. A. 1965. Statistical Theory and Methodology in Science and Engineering. New York: John Wiley & Sons.
  • Conover, W. J. 1980. Practical Nonparametric Statistics. 2nd ed. New York: John Wiley & Sons.
  • Daniel, Wayne W. 1978. Applied Nonparametric Statistics. Boston: Houghton Mifflin.
  • Daniel, Wayne W. 1995. Biostatistics. 6th ed. New York: John Wiley & Sons.
  • Hollander, M. and Wolfe, D. A. 1973. Nonparametric Statistical Methods. New York: John Wiley & Sons.
  • Lehmann, E. L. 1975. Nonparametrics: Statistical Methods Based on Ranks. San Francisco: Holden-Day.
  • Miller, Rupert G. Jr. 1996. Beyond ANOVA, Basics of Applied Statistics. 2nd. ed. London: Chapman & Hall.
  • Rosner, Bernard. 1995. Fundamentals of Biostatistics. 4th ed. Belmont, California: Duxbury Press.
  • Sokal, Robert R. and Rohlf, F. James. 1995. Biometry. 3rd. ed. New York: W. H. Freeman and Co.
  • Zar, Jerrold H. 1996. Biostatistical Analysis. 3rd ed. Upper Saddle River, NJ: Prentice-Hall.

Examine the glossary.

Back to StatGuide home page.

Get Adobe to read our PDF evaluation docs.
 

Satisfaction Guaranteed!

If you are unsatisfied with your purchase, you may return it within 30 days for an exchange, credit or refund. This guarantee does not cover electronic download products, special requests requiring photocopying or engineering aids; however, if you cannot edit our document(s) in your MS Word, Excel or Visio program we will fix it or give you a refund.

Can't find what you're looking for...?
Please call, Fax or Email Us at:

Office: (719) 649-4242
Fax: (719) 573-4205
Home Page

Click here to bookmark At-PQC™ then visit our Toolbox to find a quality control plan that will help you achieve an effective and efficient business infrastructure that focuses on customer satisfaction, continuous improvement and desirable cost savings. Visit with us today for comprehensive assistance in developing or choosing the right quality control plan for your business. Click here to visit our extensive selection of quality control plans, policies, procedures and forms or click here for help with where-to-start.

 

We can interact with you anywhere in the USA from 8:00am to 5:00pm Monday through Friday except holidays.

At-PQC™
JnF Specialties, LLC
664 Greenscape Lane
Colorado Springs, Colorado 80916-5534
Office: (719) 649-4242
Fax: (719) 573-4205
Email Us at:

Send an email to request next-day support or call our helpline at 719-649-4242 during your office hours Mon - Fri except holidays.

Click here to let us know how we're doing.

Get Adobe | About Us | Site Map | Contact Us | Privacy Policy
Policies | Procedures | FAA | Forms | Kits | ISO | Gov
Copyright © 1998-2005 JnF Specialties, LLC. All rights reserved.