Statistical Ecology
Stat 555

Goals: 

1) To test for the assumptions of ANOVA
2) To conduct one and two-way analyses of variance
3) To conduct main effects and interaction plots

A. One-Way ANOVA (date file: cowry2.MPJ)

Purpose: to examine size variation in snake head cowries (Cypraea caputserpentris). among six populations. Refer to Tissot, 1984 from additional information on samples if needed.

Data: Length of 35 cowries shells was measured in each of six populations in mm.

1. Test the data for the assumptions of ANOVA (normality and equal variances) and transform if needed. If the assumptions cannot be met complete the analyses anyway.
2. Analyze the data with a one analysis of variance using the one-way command  and a Tukey multiple range test
3. Provide a complete statistical and biological interpretation of the results based on the Guide for Writing Up Assignments.

B. Two-way ANOVA (data file: algal_freq.mpj)

Purpose: to determine if the frequency of intertidal drift seaweeds varied among populations (Santa Cruz Island and Ano Nuevo Island in California) and along wave exposure gradients at each population.

Data: Frequency was estimated as the proportion of days drift algae was present along two intertidal transects at each site relative to the total number of days surveyed and thus varied from 0-1 during 1988-1990.

1. Test the data for the assumptions of ANOVA and transform if needed. If the assumptions cannot be met complete the analyses anyway.
2. Analyze the data with a two-way analysis of variance using the GLM command (unequal samples).
3. Complete main effects and interaction plots.
4. Provide a complete statistical and biological interpretation of the results.

This assignment is due next Friday, 9/4,  in class