Advanced Statistics - Biology 6030
Bowling Green State University, Fall 2017
General Linear Models - Lab Exercises
Exercise 1: Descriptive statistics
- Download the file "CichlidEyeSize_GLM.txt".
Save the content of the file as a TEXT file and you will be able
to view and edit it with any text editor, such as BBEdit. Note
that there are 216 rows representing single individuals of different
species of cichlids of the African Great Lakes. The file contains
6 variables for each individual, namely the lake it came from
(LAKE), ecological classification with respect to feeding (TROPHIC),
sex (SEX: M=0, F=1), depth (DEPTH), standard length (STANDLEN), and eye diameter (EYEDIAM).
Note, this is a subset of the data used in a series of publications:
- van Staaden MJ, R Huber, LS Kaufman, & K Liem. 1995.
Brain evolution in cichlids of the African Great Lakes: brain
and body size, general patterns and evolutionary trends. ZACS
- Huber R, MJ van Staaden, LS Kaufman, & K Liem. 1997.
Microhabitat use, trophic patterns, and the evolution of brain
structure in African cichlids. Brain, Behav. Evol 50: 167-182
- Exam whether the
dependent variables - STANDLEN and EYEDIAM are suitable for parametric
analyis. What are your conclusions?
Exercise 2: Does size vary with sex
- Statistically test whether body size (STANDLEN) differs between
sexes (1 - female, 0 - male).
- What method do you use? What are the assumptions of this
method? Are these assumptions met?
- Perform the analysis using your favourite statistics program
and report these results along with your conclusions.
Exercise 3: Does size vary with respect to lake, feeding
type, or an interaction between the two
- Statistically test whether body size (STANDLEN) differs among
lakes, or feeding types. Perform separate analyses with lake and feeding type as factors. Report the results and explain your
- Perform a two-way, complete model Analysis of Variance using your favourite statistics program.
Report the results as an ANOVA table and explain your
conclusions. Compare the results from this full-model 2-way analysis to the two 1-way models from part 1.
Exercise 4: Does variation in eyesize relate to body size?
- Explain your view on how the two variables are causally related.
- What analysis would you use to examine the relationship.
Why is your method applicable?
- Perform the analysis using your favourite statistics program.
Report the results and explain your conclusions.
last modified: 2/27/14
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