# Different Outcomes of the Wilcoxon—Mann—Whitney Test from Different Statistics Packages

@article{Bergmann2000DifferentOO, title={Different Outcomes of the Wilcoxon—Mann—Whitney Test from Different Statistics Packages}, author={Reinhard Bergmann and John Ludbrook and Will Spooren}, journal={The American Statistician}, year={2000}, volume={54}, pages={72 - 77} }

Abstract The Wilcoxon—Mann—Whitney test enjoys great popularity among scientists comparing two groups of observations, especially when measurements made on a continuous scale are non-normally distributed. Triggered by different results for the procedure from two statistics programs, we compared the outcomes from 11 PC-based statistics packages. The findings were that the delivered p values ranged from significant to nonsignificant at the 5% level, depending on whether a large-sample…

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## References

SHOWING 1-8 OF 8 REFERENCES

Why Permutation Tests are Superior to t and F Tests in Biomedical Research

- Mathematics
- 1998

Abstract A survey of 252 prospective, comparative studies reported in five, frequently cited biomedical journals revealed that experimental groups were constructed by randomization in 96% of cases…

Nonparametrics: Statistical Methods Based on Ranks

- Mathematics
- 1975

Rank Tests for Comparing Two Treatments.- Comparing Two Treatments or Attributes in a Population Model.- Blocked Comparisons for Two Treatments.- Paired Comparisons in a Population Model and the…

Nonparametric Statistics for the Behavioral Sciences.

- Economics
- 1956

This is the revision of the classic text in the field, adding two new chapters and thoroughly updating all others. The original structure is retained, and the book continues to serve as a combined…

MICROCOMPUTER STATISTICS PACKAGES FOR BIOMEDICAL SCIENTISTS

- MedicineClinical and experimental pharmacology & physiology
- 1995

This review covers only those microcomputer statistics packages that appear to be popular with biomedical investigators who deal with fairly small sets of data but may wish to use relatively complex analytical techniques.

On a Test of Whether one of Two Random Variables is Stochastically Larger than the Other

- Mathematics
- 1947

Individual Comparison by Ranking Methods,

- 1943

Why Permutation Tests are Superior

- 1998