How do you explain that ? There's only one operator but the mixed model returns an estimate for the operator random effect. Furthermore the sample effect is confounded with the interaction sample:operator. Below is the R code and SAS give the same results.

How do you explain that ? There's only one operator but the mixed model returns an estimate for the operator random effect. Furthermore the sample effect is confounded with the interaction sample:operator. Below is the R code.

For those who are more familiar with SAS the corresponding code is:

PROC MIXED DATA=dd;
CLASS sample operator;
MODEL y=;
RANDOM sample operator sample*operator;
RUN;

This is nothing but the crossed 2-way ANOVA with random effects.