Jump to content


Photo

omega matrix

random effect

  • Please log in to reply
2 replies to this topic

#1 Crystal

Crystal

    Newbie

  • Members
  • Pip
  • 7 posts

Posted 22 June 2022 - 08:38 AM

Dear all,
I am confused about how to determine whether to use diagonal omega matrix or a full block omega matrix when attempting to converge a population PK model. which plot or Table in the output panel can I use to
determine?
I cannot find the answer in the User's Guide. Does anyone know it?
Thank you very much.



#2 smouksassi1

smouksassi1

    Advanced Member

  • Members
  • PipPipPip
  • 200 posts
  • LocationMontreal

Posted 22 June 2022 - 08:50 AM

if you data support fitting full omega go for it also use newer engines like QRPEM

 

you can then look at the omega and its standard error and also look at the computed correlation and shrinkages

 

then you can simplify your omega matrix if you see some off diagonals to be very small and not needed.

 

you can do a likelihood ratio test for off diagonal elements of omega

 

for variance components have a look at :
https://www.research..._effects_models



#3 Crystal

Crystal

    Newbie

  • Members
  • Pip
  • 7 posts

Posted 23 June 2022 - 12:57 AM

if you data support fitting full omega go for it also use newer engines like QRPEM

 

you can then look at the omega and its standard error and also look at the computed correlation and shrinkages

 

then you can simplify your omega matrix if you see some off diagonals to be very small and not needed.

 

you can do a likelihood ratio test for off diagonal elements of omega

 

for variance components have a look at :
https://www.research..._effects_models

 

Thanks a lot for your help, smouksassi1,I really appreciate it.

I still have a question regarding how to determine"some off diagonals to be very small and not needed",is there a criteria?

Thank you~~

 






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users