SPSSX Discussion

Covariates

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freek kuper

Covariates

Hi all,

I have one last question concerning covariates.

To test covariates in a linear regression I made two models. SPSS -> Analyze -> regression -> Linear. First the dependent variable with the covariates. I pressed next in spss and then put the independent variables in the model.

I need to check the adjusted R² because I have two independent variables and three covariates.

But what if the adjusted R² is a negative number. Does that mean it’s zero and it doesn’t explain any of the variation? And what if the adjusted R² for the covariates is 0.054 and with the independent variables added it is 0.074. What does this mean? That my independent variables explained 2% of the variation?

I need to evaluate my model with these covariates. But I’m not sure what is good and what is bad.

Freek

Verzonden vanuit Mail voor Windows 10

Van: [hidden email]
Verzonden: donderdag 7 januari 2016 17:17
Aan: [hidden email]
Onderwerp: Re: what is the story!

Re the random numbers it sounds like you have it right. Example below.

**************************************************.
DATASET CLOSE ALL.
OUTPUT CLOSE ALL.

DATA LIST FREE / X.
BEGIN DATA
1
2
3
4
5
6
7
8
9
10
END DATA.

DEFINE !RandSamp ()
!DO !I = 1 !TO 3
TEMPORARY.
SAMPLE 2 FROM 10.
LIST X.
!DOEND
!ENDDEFINE.

SET SEED 10.
!RandSamp.
*2,10|3,9|5,8.

*This is different.
!RandSamp.
*8,9|3,10|4,7.

*This is same as orig.
SET SEED 10.
!RandSamp.
*2,10|3,9|5,8.

DEFINE !RandSamp2 ()
!DO !I = 1 !TO 3
SET SEED 11.
TEMPORARY.
SAMPLE 2 FROM 10.
LIST X.
!DOEND
!ENDDEFINE.

*This produces same for each iteration.
!RandSamp2.
*3,9|3,9|3,9.
**************************************************.

It seems to me your hang up with the editor is it wants to run whole DO-IF
blocks and whole DEFINE-!ENDDEFINE blocks. Alittle annoying I guess but not
the end of the world.

-----
Andy W
[hidden email]
http://andrewpwheeler.wordpress.com/
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Art Kendall

Re: Covariates

Art Kendall
Social Research Consultants

freek kuper

Re: Covariates

In reply to this post by freek kuper

Hi,

My sample size is 30, but I’m testing 12 variables each, in which spss thinks that I have 360 persons.

There are no cases missing.

Freek

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Van: [hidden email]
Verzonden: donderdag 7 januari 2016 18:31
Aan: [hidden email]
Onderwerp: Re: Covariates

How many cases do you have?

Are there missing data?
Does missingness eliminate many cases?

It is good practice to use the GUI only to draft your syntax. As you under
stand your data and your analysis you will inevitably need to redraft your
syntax.

Please go through the GUI steps but exit via <paste>. Then post your
syntax.

-----
Art Kendall
Social Research Consultants
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Art Kendall

Re: Covariates

It sounds like you have some sort of repeated measures.

What are your design (predictor, independent) variables? What are their levels of measurement?

what are your dependent (output, predicted) variables?

What constitutes a case? (the 30) How were they selected?

What is the nature of your repeats for each case (the 12)?

Art Kendall
Social Research Consultants

David Marso

Re: Covariates

Administrator

Art,
Here is where that rabbit hole begins:
http://spssx-discussion.1045642.n5.nabble.com/Beginner-is-stuck-with-SPSS-td5731171.html
Let the fun continue....
OP: Please review the distinction between independent samples and repeated measures.
Please review the assumptions of the linear regression model re independence of observations.
You are screwing the pooch on the latter.
--

Art Kendall wrote

It sounds like you have some sort of repeated measures.

What are your design (predictor, independent) variables? What are their levels of measurement?

what are your dependent (output, predicted) variables?

What constitutes a case? (the 30) How were they selected?

What is the nature of your repeats for each case (the 12)?

Please reply to the list and not to my personal email.
Those desiring my consulting or training services please feel free to email me.
---
"Nolite dare sanctum canibus neque mittatis margaritas vestras ante porcos ne forte conculcent eas pedibus suis."
Cum es damnatorum possederunt porcos iens ut salire off sanguinum cliff in abyssum?"

Art Kendall

Re: Covariates

David thanks for the "heads up"

Art Kendall
Social Research Consultants

freek kuper

Re: Covariates

In reply to this post by freek kuper

Hi guys,

I’m sorry for the trouble, but I’ve got it! Went to someone who has a lot of knowledge of spss and statistics. He was busy actually and wouldn’t have time for me. So that’s why I set up a quick e-mail. Panicked a bit there. But it’s alright now. He got some free time to help me. It’s really more convenient to explain your problem face to face instead of via e-mail.

Sorry for the trouble and thanks a lot for all your help and time!

Freek

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Van: [hidden email]
Verzonden: donderdag 7 januari 2016 19:12
Aan: [hidden email]
Onderwerp: Re: Covariates

Art,
Here is where that rabbit hole begins:
http://spssx-discussion.1045642.n5.nabble.com/Beginner-is-stuck-with-SPSS-td5731171.html
Let the fun continue....
OP: Please review the distinction between independent samples and repeated
measures.
Please review the assumptions of the linear regression model re independence
of observations.
You are screwing the pooch on the latter.
--

Art Kendall wrote

> It sounds like you have some sort of repeated measures.
>
> What are your design (predictor, independent) variables? What are their
> levels of measurement?
>
> what are your dependent (output, predicted) variables?
>
> What constitutes a case? (the 30) How were they selected?
>
> What is the nature of your repeats for each case (the 12)?

-----
Please reply to the list and not to my personal email.
Those desiring my consulting or training services please feel free to email me.
---
"Nolite dare sanctum canibus neque mittatis margaritas vestras ante porcos ne forte conculcent eas pedibus suis."
Cum es damnatorum possederunt porcos iens ut salire off sanguinum cliff in abyssum?"
--
View this message in context: http://spssx-discussion.1045642.n5.nabble.com/Covariates-tp5731221p5731227.html
Sent from the SPSSX Discussion mailing list archive at Nabble.com.

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