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  • 1.  Mixed Regression not working

    Posted Wed May 31, 2023 10:15 AM

    Hello and thank you for taking the time to help me!
    I want to run a mixed regression on some data that I collected, but whenever I run my syntax the SPSS either shuts down immediately or just tells me that it is running the procedure but it never produces an output. ( I will provide some more details on what I have tried further below).

    About the data:
    I collected data from 29 participants, each participant completed 5 blocks of a behavioral task, and the dependent variables that I want to investigate are reaction time (continuous) and correct (binary). Around 50.000 trials in total.

    Now within each block there were 336 trials. Each trial could be allocated to a condition based on several factors:
    - SWITCH: 3 levels
    - Task: 4 levels
    -  Congruency: 7 levels
    - Block: 5 levels (as mentioned above)

    The design was balanced and after removing some outliers remains almost perfectly balanced ( I also tried all analyses without outlier removal without any difference).

    Now what was my plan:
    I wanted to run a mixed regression, starting with ARMA(1,1), the slowly reduce the complexity of the covariance matrix, and then look at the fixed effects.

    The Syntax I was using:

      MIXED log_RT BY SWITCH Congruency Task Block
      /FIXED=SWITCH*Congruency SWITCH*Task SWITCH*Block Congruency*Task Congruency*Block Task*Block SWITCH Congruency Task Block | SSTYPE(3)
      /REPEATED=trialnb_overall | SUBJECT(sbj) COVTYPE(ARMA11).
    As mentioned above when I run the analysis above SPSS stops running ( however it never takes up more than 15% of the computational power of my PC: specs  (16Go RAM, Intel Core i7, 500Go  SSD, Nvidia Quadro P620). 

    When I run the same analysis on a 10% subset of the data I get a warning that the Covariance matrix did not converge, or that the Hessian is not positive definite.

    So, first of all ... sorry for the long text ... I hope this makes the issue clear.

    I am not quite sure whether the issue is that my data is too big or if I am not doing the analysis that I was wanting to do. 

    I would be very grateful for any kind of advice.

    Kind Regards,

    your fellow lost PhD student.

    Marcel Hinss

  • 2.  RE: Mixed Regression not working

    Posted Wed June 07, 2023 11:35 AM
    Edited by David Dwyer Wed June 07, 2023 11:35 AM

    Hi @Marcel Hinss 

    I asked a couple of our statisticians to take a look at your query and provide some observations.  Here is the result:

    We had a discussion regarding the query on Mixed Regression not working and we have come up with the following observations :
      1. Why the client choose ARMA(1,1)? Is it a time series data? Did he check whether data set satisfies the requirements of ARMA(1,1)? 
      2. If the ARMA conditions are not satisfied with the dataset, then we suggest to proceed with other types of covariance such as Compound symmetry, etc.                                                                                             
      3. We also suggest increasing the number of iterations.
    Another suggestion is to apply other methods of outlier detection.
    You have indicated that you are a PhD student.  Perhaps the best place for you to begin will be with the Methodologist on your Dissertation committee.  That person will best be able to help you with a research design and correct analytic techniques to match.

    David Dwyer
    SPSS Technical Support
    IBM Software

  • 3.  RE: Mixed Regression not working

    Posted Thu June 22, 2023 03:08 AM

    Dear David, 

    thank you very much for your support! In fact the data is a Time series. IIncreasing the number of iterations had the expected outcome and now the algorithm converges. Thank you very much again for your support I hope you have a great week.

    Kind Regards,


    Marcel Hinss