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Unconditional Linear Growth Model using SPSS

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E. Bernardo

Unconditional Linear Growth Model using SPSS

Below is the spss syntax for unconditional linear growth model.

mixed SE with Time

/fixed = intercept time

/random intercept time | subject(id) covtype(un)

/print=solution testcov

/method ml.

We have 2 time points (Time=0 and Time=1) with n=165. SPSS computes the parameter estimates, except the covariance estimate for UN(2,2). A note appeared as "This covariance parameter is redundant. The test statistic and confidence interval cannot be computed.". Can someone comment why the estimate for UN(2,2) cannot be computed? What is meant by "covariance parameter is redundant"?

Thank you.

Eins

David Marso

Re: Unconditional Linear Growth Model using SPSS

Administrator

Read up on parameterization of linear models?
--

E. Bernardo wrote

Below is the spss syntax for unconditional linear growth model.

mixed SE with Time
/fixed = intercept time
/random intercept time | subject(id) covtype(un)
/print=solution testcov
/method ml.

We have 2 time points (Time=0 and Time=1) with n=165. SPSS computes the parameter estimates, except the covariance estimate for UN(2,2). A note appeared as "This covariance parameter is redundant. The test statistic and confidence interval cannot be computed.". Can someone comment why the estimate for UN(2,2) cannot be computed? What is meant by "covariance parameter is redundant"?

Thank you.
Eins

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Swank, Paul R

Re: Unconditional Linear Growth Model using SPSS

In reply to this post by E. Bernardo

You are trying to estimate three random coefficeints with only two data points per subject.

Paul R. Swank, Ph.D., Professor
Health Promotions and Behavioral Sciences
School of Public Health
University of Texas Health Science Center Houston

________________________________
From: SPSSX(r) Discussion [[hidden email]] On Behalf Of E. Bernardo [[hidden email]]
Sent: Thursday, December 27, 2012 3:06 AM
To: [hidden email]
Subject: Unconditional Linear Growth Model using SPSS

Below is the spss syntax for unconditional linear growth model.

mixed SE with Time
/fixed = intercept time
/random intercept time | subject(id) covtype(un)
/print=solution testcov
/method ml.

We have 2 time points (Time=0 and Time=1) with n=165. SPSS computes the parameter estimates, except the covariance estimate for UN(2,2). A note appeared as "This covariance parameter is redundant. The test statistic and confidence interval cannot be computed.". Can someone comment why the estimate for UN(2,2) cannot be computed? What is meant by "covariance parameter is redundant"?

Thank you.
Eins

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