I am trying to identify outliers by plotting conditionally externally studentized residual against predicted values obtained from fitting mixed model in SAS using PROC MIXED as follows:

proc mixed data = breed_trans noitprint noinfo noclprint covtest update;

by trial_type year loc trial trait;

class rep gen ;

model y = /ddfm = kr outp= dm_studenres influence;

random rep gen;

ods listing exclude solutionR fitstatistics ;

ODS output covparms= dm_para(drop = StdErr ZValue ProbZ);

where trait in("dm");

run;

quit;

The analysis was done for individual trial across different breeding stage over over year and location. My studentized seemed to be very high, varied from 10 to - 20. I would like to know if the influence option gives me the correct studentized residual. which is better to use between internally and externally studentized residual for outlier detection.

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