Re: logistic regression question

Thanks for the ideas, folks.

What I have ended up doing is dividing each individual's sequence into
a first half and a second half, calculating the proportion of A
responses in each half, and then just doing a paired comparison test
over all the individuals (you can do a paired t-test but I prefer
Fisher's paired comparison randomisation test).

The only thing I don't like about this is that one can claim it is
somewhat arbitrary to cut the sequences in half, rather than divide
them in any other way. But my p value is so strongly significant that
it is difficult to argue I am fiddling anything.

One thing I didn't mention before, which complicates things and made
some of the suggestions (like the Cochran test) impossible, is that
not all individuals perform the same number of actions, so the
sequences are of different lengths. Actually, while experimenting with
logistic regression, I found that variable sequence lengths had a
rather undesirable effect:

If you generate random sequences of varying lengths for individuals,
with a different but constant p(A)=1-p(B) for each individual, and
then run a logistic regression model: outcome = individual + sequence
position, you will get a significant effect (i.e. p < 0.05) of
sequence position far more often than 5% of the time. Something is
clearly wrong! It seems to be because the ends of long sequences have
too much influence on the model - say p(A) for the longest sequence is
0.1 but the mean p(A) earlier on is higher, the mean p(A) will drop
over the sequence but that is because higher p(A) individuals are
dropping out. This shouldn't result in a significant effect of
sequence position, but it does!

No doubt I have misunderstood something badly!

Cheers,

Ben
.

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