Re: logistic regression question

On Feb 1, 8:03 am, amorphia <spam.onto...@xxxxxxxxx> wrote:
I have an experimental design where subjects make a sequence of simple
binary choices A or B. I would like to test the hypothesis that
initially in the sequence subjects tend to choose A, but this bias
degrades to random (or perhaps a bias to B) as the sequence
progresses.

Initially I thought that maybe I could do a simple binary logistic
regression, with sequence position as the only covariate. But now I
think that this is probably invalid, because this would assume that
choices at sequence position t+1 are independent of choices at
sequence t. This assumption is plainly false because the choices are
made by the same individuals who may make runs of the same choice.

Can I solve this problem by including individual as a factor in the
model perhaps? Or is a more complicated solution necessary?

Yes, making the additive constant in the logistic equation
person-specific, so that it becomes 'a_i' instead of just 'a',
would be one way to attack the problem.

Another approach would be to use Cochran's Q test -- don't omit
the df-adjustment for non-sphericity -- with pairwise McNemar
tests on the positions.
.

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