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02-12-2018 01:12 PM - last edited on 02-12-2018 01:24 PM by ChrisHemedinger

Could anyone help me understand following two lines?

* random intercept / subject=trial1(subjectid group);

--> Does it mean to report the variance due to a variable "trial"?

--> Is there a possibility that "trial" was treated as "repeated" variable in proc glimmix through this code, because proc glimmix does not have repeated statement?

* random _residual_ / group=slc;

--> I think I have a vague sense that residuals are divided by the level of slc through this code, but I am not quite understanding why we divide them. How does it take care of heteroscedasticity problem?

Thanks in advance.

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Posted in reply to nlpurumi

02-12-2018 01:25 PM - edited 02-12-2018 01:25 PM

You need to post more code.

What PROC is this part of for starters?

nlpurumi wrote:

Could anyone help me understand following two lines?

* random intercept / subject=trial1(subjectid group);--> Does it mean to report the variance due to a variable "trial"?--> Is there a possibility that "trial" was treated as "repeated" variable in proc glimmix through this code, because proc glimmix does not have repeated statement?* random _residual_ / group=slc;--> I think I have a vague sense that residuals are divided by the level of slc through this code, but I am not quite understanding why we divide them. How does it take care of heteroscedasticity problem?Thanks in advance.

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Posted in reply to Reeza

02-12-2018 04:40 PM - edited 02-12-2018 04:42 PM

Because I received a help on this matter through other route, I want to ask a different question.

I want to build SAS code to test following equations:

Level 1 equation: Yij=β0j+β1j(SLC)+β2j(T)+β3j(SLC*T)+ rij(error) (i: individual, j: each group) Level 2 equations: β0j= γ00+ γ01(G)+u0j β1j= γ10+ γ11(G)+u1j β2j= γ20+ γ21(G)+u2j β3j= γ30+ γ31(G)+u3j

Will this be the good enough codes?

proc mixed data=dissertation1 ic;

class group slc subjectid trial1;

model ISI_Avg_sqrt= group|slc /ddfm=kr2 outp=R;

random intercept / subject=subjectid(group);

random slc / subject=subjectid(group);

random intercept / subject=trial1(subjectid group);

repeated /group=trial1;

/*repeated / group=slc;*/

run;

Thanks in advance!