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MANE 6313

Week 4, Module G

Student Learning Outcome

Analyze simple comparative experiments and experiments with a single factor.

Module Learning Outcome

Apply the Kruskal-Wallis test for one-way analysis of variance when the data is not normally distributed.

Dispersion Effects

  • Previous analyses have focused on location effects

  • Researchers should be concerned with dispersion effects

  • The response variable for dispersion effect is usually \(\log(s)\) or \(\log(s^2)\) or \(-\ln(s)\)

  • Consider the problem given in table 3-16 on page 99

Kruskal-Wallis Test

  • A non-parametric alternative to the one-way ANOVA

  • Test is based upon the rank (order) of the observations, not their values

  • Used when the normality assumption is not satisfied

  • Not as powerful for normally distributed data

Kruskal-Wallis Test

Krusdal-Wallis Test

R Demonstration

  • Kruskal-Wallis Test