# repeated measure ANOVA and covariate

#### kukuzry

##### New Member
There are 55 subjects measured in two stages. The variable is called V1. There is another variable called V2 (dichotomies). Some values of V2 are different in Stage 1 and Stage 2.

I want to compare means between V1 and V2. Normally, I can use one way repeated measures in SPSS.

In addition, I also want to analyze whether the V2 affects the means or not. How can I do this analysis? Initially, I hope to regard V2 as a covariate in the one way repeated measures ANOVA in SPSS, but Some values of V2 are different in the two stages for the same subjects. It seems not suitable to use covariate? Am I right? So how can I conduct this analysis in SPSS? Thanks.

EDIT:

>>> Some values of V2 are different in Stage 1 and Stage 2.
------ Explain: I mean V2 are not constant in the two stages. For example, for Subjects 1, 5, 10, in Stage 1, V2 = 10 (subject 1), 15 (subject 5), 17 (subject 10), but in Stage 2, V2 = 11 (subject 1), 13 (subject 5), 16 (subject 10). V2 are changing with the time.

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#### kukuzry

##### New Member
>>> Some values of V2 are different in Stage 1 and Stage 2.
------ Explain: I mean V2 are not constant in the two stages. For example, for Subjects 1, 5, 10, in Stage 1, V2 = 10 (subject 1), 15 (subject 5), 17 (subject 10), but in Stage 2, V2 = 11 (subject 1), 13 (subject 5), 16 (subject 10). V2 are changing with the time.

>>> but Some values of V2 are different in the two stages for the same subjects.
------ The explanation is shown above.

Thank you,

#### kukuzry

##### New Member
Thanks. But how can a variable be constant in the first place? What was the implication of this part of information?

Thanks. Ok, as you have defined V2, it is already a variable. A covariate as well is a variable. It is not a constant. Then why changes in a variable (V2) is something that might disallow you to pick it as a covariate?
In SPSS, I do not know to where to input the covariate. Please see the attached image.

V1 is divided into two variables: UnitAA and P2UnitAA: which are the measured variables in two stages separately. Therefore, there are 55 cases for each variables. How can I input the covariate V2 in this dialogue? V2 has 110 cases (in two stages). I think V2 is variable because it is like between subject factor and for the same subject, V2 does not chagne, for example, V2 is gender, different subjects have different genders but in the two stages, gender does not change. Am I right? I do not know where to input V2 in SPSS.

#### victorxstc

##### Pirate
>>> Some values of V2 are different in Stage 1 and Stage 2.
------ Explain: I mean V2 are not constant in the two stages. For example, for Subjects 1, 5, 10, in Stage 1, V2 = 10 (subject 1), 15 (subject 5), 17 (subject 10), but in Stage 2, V2 = 11 (subject 1), 13 (subject 5), 16 (subject 10). V2 are changing with the time.
Thanks. But how can a variable be constant in the first place? What was the implication of this part of information?

Initially, I hope to regard V2 as a covariate in the one way repeated measures ANOVA in SPSS, but Some values of V2 are different in the two stages for the same subjects. It seems not suitable to use covariate?
Thanks. Ok, as you have defined V2, it is already a variable. A covariate as well is a variable. It is not a constant. Then why changes in a variable (V2) is something that might disallow you to pick it as a covariate?

-----------------------

Am I right? I do not know where to input V2 in SPSS.
Like other "variables", covariates as well can vary over time (or be constant).

For inputting a time-dependent covariate in a repeated-measures ANOVA, consult this link (see model 3) or Google it.

#### kukuzry

##### New Member
Like other "variables", covariates as well can vary over time (or be constant).

For inputting a time-dependent covariate in a repeated-measures ANOVA, consult this link (see model 3) or Google it.
Many thanks!! I will look at it!

#### kukuzry

##### New Member
Hi, I am not familiar with Mixed model. I saw some tutorial and define some parameters here. Am I right? Thank you,

Q83 is the covariate.

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