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Re: analyzing change for one dichotomous variable, assessed at pre and post

Posted by Kornbrot, Diana on May 06, 2012; 5:21am
URL: http://spssx-discussion.165.s1.nabble.com/analyzing-change-for-one-dichotomous-variable-assessed-at-pre-and-post-tp5688136p5688798.html

classic solution is mcnemar test
test
y-n/(y-n + n-y) > .5
use exact binomial if n switchers small people wio do not chane irrelevant
best
diana

Sent from my iPhone

On 6 May 2012, at 05:36 AM, "pji" <[hidden email]> wrote:

> I have a situation where I have one variable, smoking yes/no, taken at pre
> then taken at post, few years later. n ~70. same participants at both pre
> and post. the possible combinations are
>
> smoking     pre       post
>                 y          y
>                 n          n
>                 y          n
>                 n          y
>
> goal is to determine if the percentage of participants who changed from Y
> smoking at pre to N smoking at post is significant.
>
> I don't think any sophisticated analysis has to be conducted. I would simply
> assign the four possible outcomes to four categories (y - y, n - n, y - n, n
> - y) and then run a chi-square to determine if the observed frequency counts
> of those four categories are different from the expected frequency counts.
> there is no post-hoc test, so I would have to heuristically examine which
> categories have the most deviance.
>
> are there any analyses that could be conducted?
> thank you in advance.
> pj
>
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