data post age correction

[Arianm]

Dear all,
I have a question about how to show my new data post-age correction.
So imagine, protein A is different between group 1, 2 and 3. However these groups differ in age, so we have to perform age corrections (I do this with GLM--> univariate --> covariate: age)
now my question is how to depict the data after this age correction in a box plot? so one of the methods I was considering was to save: unstanderdized predicte values, and then do the box plot with the new saved data. However i am not certain if this method is correct, and if not, how should I perform this task?

Thank you in advanced

Kind regards
Arjan

[Bruce Weaver]

I don't have time to respond to this right now...this reply is just an attempt to get your question posted to the mailing list.  (It has been visible in the Nabble archive since early this morning, but there is a warning message that says it has not been delivered to the mailing list yet.  Perhaps this will get it out to the list.)

Arianm wrote

Dear all,
I have a question about how to show my new data post-age correction.
So imagine, protein A is different between group 1, 2 and 3. However these groups differ in age, so we have to perform age corrections (I do this with GLM--> univariate --> covariate: age)
now my question is how to depict the data after this age correction in a box plot? so one of the methods I was considering was to save: unstanderdized predicte values, and then do the box plot with the new saved data. However i am not certain if this method is correct, and if not, how should I perform this task?

Thank you in advanced

Kind regards
Arjan

[Ian Martin-2]

Arjan,

You do not say if the ANCOVA is defensible.  Did you check the treatmentXcovariate interaction term?  Without homogeneity of slopes, the adjustment is meaningless.  You said age differs between groups, and this is also potentially a problem if the differences are significant.  

Was Levene's test OK too?

I have seen -- too often -- situations where researchers blithely "adjust" for many covariates without first checking to see if it is possible.

regards,
Ian

On Sep 2, 2014, at 5:49 AM, Arianm <[hidden email]> wrote:

> Dear all,
> I have a question about how to show my new data post-age correction.
> So imagine, protein A is different between group 1, 2 and 3. However these
> groups differ in age, so we have to perform age corrections (I do this with
> GLM--> univariate --> covariate: age)
> now my question is how to depict the data after this age correction in a box
> plot? so one of the methods I was considering was to save: unstanderdized
> predicte values, and then do the box plot with the new saved data. However i
> am not certain if this method is correct, and if not, how should I perform
> this task?
>
> Thank you in advanced
>
> Kind regards
> Arjan
>
>
>
> --
> View this message in context: http://spssx-discussion.1045642.n5.nabble.com/data-post-age-correction-tp5727132.html
> Sent from the SPSSX Discussion mailing list archive at Nabble.com.
>
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