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st: ANOVA model


From   David Airey <david.airey@Vanderbilt.Edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: ANOVA model
Date   Sat, 28 Sep 2002 09:57:53 -0500

Dear List,

I am having trouble deciding on the right Stata command to estimate the following ANOVA model:
----------------------------------------------------------------------
Animal 1 2 3 4 5
/ \ / \ / \ / \ / \
Location 1 2 1 2 1 2 1 2 1 2
/ \ / \ / \ / \ / \ / \ / \ / \ / \ / \
Neuron 01-03 04-06 07-10 11-12 13-15 16-18 19-21 22-24 25-27 28-30
----------------------------------------------------------------------

In this design, we have as sources of variation, different neurons measured from the same location in the brain, different locations, and different animals:

= population mean
a = animal effect
l = location effect
n = neuron effect <- this might just be in the error
e = error

or the measure for a neuron Y = + a + l + (n + e)

So I think I should have a fixed effect for location (we are interested in the mean difference between locations and we assigned the locations) and two random effects, one for animal, and one for replicate neurons (random because we are not interested really in the mean differences but just accounting for the variance and because they are animals or neurons selected from a larger population, presumably with equal probability). I am guessing I need to nest neuron in location and treat animal as a random block effect, but at usual, can decide on the proper test constructions.

Any thoughts?

-Dave
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