If she is just using the difference initial and final measurements then it
is a paired comparisons design and the degrees of freedom are 6-1 = 5.
Basically the t-test is a one-sample test using the 6 differences as the raw
data.
This is a special case of what is called repeated measures which could be
used to analyse all 5 repeats but that is another story entirely.
--
--------------------------------------------
Dr Graeme Byrne
Division of Mathematics
La Trobe University, Bendigo
Ph: 61 3 5444 7263
Fax: 61 3 5444 7998
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