Hi folks,
Let's say you have a repeatable experiment and each time the result can be
classed into a number of discrete categories (in this real case, seven).
If a treatment has no effect, it is known what the expected by chance
distribution of results between these categories would be. I know that a
good test to see if a distribution of results from a particular treatment
is different to the expected by chance distribution is to use a
chi-squared test. What I want to know is, is it valid to compare just one
category? In other words, for both the obtained and expected
distributions, summarise them to two categories, one of which is the
category you are interested in, and the other containing all the other
categories. If the chi-square result of the comparison of these categories
is significant, can you say that your treatment produces significantly
more results in particularly that category, or can you only think of the
whole distribution?
Thanks,
Ben
--
Ben Kenward Address for post:
Department of Zoology Wolfson College
Oxford University Linton Road
01865 284387 Oxford OX2 6UD
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