R

Table of Contents

1 SESSION NINE.

1.1 Analysis of Variance (ANOVA).

DOWNLOAD from the link http://www.bio.ic.ac.uk/research/mjcraw/therbook/data following files:

yields.txt

growth.txt

1.1.1 One-way ANOVA

  1. Read file yields.txt
  2. Calculate the mean yields for the three soils
  3. Make a table with two columns yield data and soils that are relative to this yield
  4. Check the constancy of variance across the three soil types: calculate the variances for each soil type

Is the variances differ by more than factor of 2? Is this difference significant?

  1. Check the homogenity of variances. What test do you need to use?
  2. Plot your data. What plot will represent your data the best?

Save your plot in pdf and eps format

  1. Compare the mean yields of different soils using analysis of variance (aov function)
  2. Check the assumptions of the aov model by plotting the model

1.1.2 Two-way ANOVA with replication (Factorial ANOVA)

  1. Read file growth.txt
  2. Calculate the mean values of weight gain per diet per supplement
  3. Plot your data
  4. Estimate parameters for the main effects of each level of diet and each level of supplement

The model is gain~diet+supplement+diet:supplement

Author: ELVIRA <kurmaevaer@titan.sfasu.edu>

Date: 2009-08-11 11:13:13 CDT

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