http://spssx-discussion.165.s1.nabble.com/Advice-on-analyzing-data-tp5700681p5701076.html
Sigh. If you did not have experts in statistics and design
involved from the start, you probably overlooked vital questions
that could have been asked for control, or you missed good
chances for getting better data. So you might have a hard
time in recruiting good, experienced, competent experts at
this late stage.
But you need to try. Someone will need to lay hands on the
data to see what the chances are. Drawing inferences is always
difficult for observational data. Your non-random control puts
your data pretty much into that class. And then there are
measurement issues that might have been avoided if the study
were "designed" in the first place.
For instance, you state, about the outcomes, that "the data
is highly skewed...." I suspect that this is a naive comment
about some set(s) of numbers. But any set of numbers
might be (perhaps) easily transformed to a different scale.
Is "skewness" inherent in the set of outcomes, as latent variables,
or is that an artifact of measurement? - If you really do have
relatively-few extreme outcomes (successes?) versus everything
else, that might reduce the power of analyses and reduce your
possibilities for doing internal replications.
--
Rich Ulrich
Date: Thu, 10 May 2012 15:27:53 +0000
From:
[hidden email]Subject: Advice on analyzing data
To:
[hidden email]
I am looking for some advice on the best approach for analyzing our data in SPSS. We are currently running version 19. We have a group of 2,405 people who received an intervention and 5,702 people who did not receive the intervention
(the groups were not randomly selected so we know we have bias in that area). For each individual, we have up to 27 months of data from the period prior to the start of the intervention and 12 months of data post-intervention. For most of the outcomes of
interest, the data is highly skewed and not normally distributed.
Thanks,
...