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 Analysing repeated measures with Linear Mixed Models

Emanuel Festino's profile image
Emanuel Festino posted Wed August 06, 2025 05:45 AM

Hi all,
I would run a repeated measures with Linear Mixed Models. In attachment you can find the following dataset. In my study, the dependent variable is jump performance (HOPPING VARIABLE). Each participant has four repeated measurements, resulting from a combination of two factors:
Time: pre and post intervention
Leg: dominant and non-dominant

If i use the residual methods, than Satterthwaite, I have this message: 

Warnings

The final Hessian matrix is not positive definite although all convergence criteria are satisfied. The MIXED procedure continues despite this warning. Validity of subsequent results cannot be ascertained.

 While if I use Satterthwaite methods, I have a great standard error in covariance parameters

Estimates of Covariance Parametersa

Parameter

Estimate

Std. Error

Wald Z

Sig.

95% Confidence Interval

Lower Bound

Upper Bound

Repeated Measures

UN (1,1)

.132

13725.211

.000

1.000

.000

.

UN (2,1)

.063

13725.211

.000

1.000

-26900.856

26900.982

UN (2,2)

.100

13725.211

.000

1.000

.000

.

UN (3,1)

.054

13725.211

.000

1.000

-26900.865

26900.972

UN (3,2)

.019

13725.211

.000

1.000

-26900.900

26900.937

UN (3,3)

.076

13725.211

.000

1.000

.000

.

UN (4,1)

.046

13725.211

.000

1.000

-26900.873

26900.964

UN (4,2)

.044

13725.211

.000

1.000

-26900.875

26900.962

UN (4,3)

.026

13725.211

.000

1.000

-26900.893

26900.944

UN (4,4)

.097

13725.211

.000

1.000

.000

.

CODICE

Variance

.099

13725.211

.000

1.000

.000

.

a. Dependent Variable: HOPPING .


Someone could help me, please?
Thanks all!
In attachment, you can find also the output of results



My goal is to evaluate whether a specific type of training intervention had an effect on jump performance, considering both leg and time as repeated factors.
I am not entirely sure how to correctly define the repeated structure in SPSS MIXED, particularly regarding the choice of covariance structure and whether the model is correctly specified for this within-subject design. I