Hi
when I read some statistical texts, they say that the one sample t test
is used to compare the mean of a population (from which your sample has
been drawn) to a hypothesized value. So my understanding of this is
that the population mean is being compared to a theoretical (non
empirical) value.
Several of the books then use examples like - suppose we know that the
mean weight of frogs is X Kg then we can use our sample of frogs to draw
an inference as to whether the population from which our frogs have been
drawn has the same mean weight.
However I presume that our 'target' weight (X kg) was itself derived
from some experiment/study and consequently is not a theoretical value,
but an estimate with an associated error.
So, my question. If you can use a one sample t test to compare a
sample's population mean to a theoretical value, can you legitimately
use it to compare your sample's population mean to a value based upon
empirical estimation - or in these circumstances do you really require
some measure of the error on the empirical mean (and then do an
independent samples t test?).
Curiously enough this issue been 'brought to my attention' twice today,
in two quite different circumstances, so it would be very helpful to
know the answer.
Best regards to you all
Thanks
Graham
--
Dr G.S.Clarke
Lecturer in Physiology & Biometry
Faculty of Health Studies
University of Wales, Bangor
Fron Heulog
Ffriddoedd Road
Bangor
Gwynedd LL57 2EF
Tel: 01248 383157
e-mail: [log in to unmask]
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