Math 225

Introduction to Biostatistics

Millipedes

A study investigated the concentration of alanine (in mg/100 ml) in males and females of three species of millipedes. (The source gives no indication on why this may be of interest.)

The raw data is here.

Summary Statistics

Summary Data of Alanine Concentration by Sex and Species
SexSpecies 1Species 2Species 3
Male21.20 (1.33)16.18 (1.67)18.53 (1.84)
Female15.08 (1.24)12.68 (1.33)13.73 (1.21)

Interaction Graphs

Show example of an interaction plot. Put one factor on the x axis and connect the corresponding levels of the other factor.

Anova Table

            Df Sum of Sq  Mean Sq  F Value     Pr(F) 
        sex  1  138.7204 138.7204 65.67942 0.0000002
    species  2   55.2608  27.6304 13.08207 0.0003103
sex:species  2    6.8908   3.4454  1.63129 0.2233107
  Residuals 18   38.0175   2.1121                   
Total       23  238.8895
Last modified: March 27, 2001

Bret Larget, larget@mathcs.duq.edu