Statistics: Detecting Differences Among Groups

Phil Robakiewicz1, Elizabeth F. Ryder1

1 Worcester Polytechnic Institute, Worcester, Massachusetts
Publication Name:  Current Protocols in Protein Science
Unit Number:  Appendix 3G
DOI:  10.1002/0471140864.psa03gs21
Online Posting Date:  May, 2001
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Abstract

Some of the statistical tests most commonly used (and misused) in biological research are presented here. The tests discussed are those used for comparisons among groups (e.g., t test and ANOVA). The purpose of this appendix is to enable the investigator to determine rapidly the most appropriate way to analyze data, and to point out some of the most common errors to avoid.

     
 
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Table of Contents

  • Basic Statistical Background
  • Choosing a Test— Exploratory Data Analysis
  • Statistical Tests for Comparisons Between Two Unpaired Groups
  • Comparing Two Paired Groups: Paired t Test, Wilcoxon Signed Rank Test, and Sign Test
  • Multiple Comparisons
  • Conclusion
  • Literature Cited
  • Figures
  • Tables
     
 
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Materials

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Figures

Videos

Literature Cited

   Siegel, S. and Castellan, N.J., Jr. 1988. Nonparametric Statistics for the Behavioral Sciences, 2nd ed. McGraw‐Hill, New York.
   Sokal, R.R. and Rohlf, F.J. 1981. Biometry, 2nd ed. W.H. Freeman, New York.
   Sokal, R.R. and Rohlf, F.J. 1987. Introduction to Biostatistics, 2nd ed. W.H. Freeman, New York.
   Zar, J.H. 1984. Biostatistical Analysis, 2nd ed. Prentice‐Hall, Englewood Cliffs, New Jersey.
Key References
   Hampton, R.E. 1994. Introductory Biological Statistics. William. C. Brown Publishers, Dubuque, Iowa.
  Provides excellent outlines for many statistical tests and uses relevant, comprehensible biological examples.
   Motulsky, H. 1995. Intuitive Biostatistics. Oxford University Press, New York.
  A nice, nonmathematical introduction to biostatistics, covering standard topics as well as many areas important to biology that are often omitted from introductory texts.
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