[R-sig-ME] FW: how do I describe heteroscedacity

Lize van der Merwe lize@t@t@ @ending from gm@il@com
Sat Aug 25 11:50:24 CEST 2018

Dear mixed-models list
Please help.
I  used lme to fit a model which includes different variances for operators.
My question is:
What is the best way to report the operator standard deviations?   
Here are the details.
My data contains an outcome, with predictors load (4 different loads) and
operator (10 different operators).  It is a very large unbalanced data set,
with some operators only working on a single load while others operated on
all 4 loads.  I am interested in the load means, the operator means and the
operator variances.  The latter is my problem.
I used the model  
lme(Outcome~Load,random=~1|Operator,weights = varIdent(form= ~ 1 |
I used intervals() to obtain estimates with 95% CIs of the effects of the
loads and the operators.   
Because of identifiability, the model yields delta, the ratio of specific
operator standard deviation to first operator standard deviation with their
95% CIs.  
The attached plot shows the deltas, with their confidence intervals.  
Is it possible to  estimate the standard deviations and their confidence
Is it correct to state that, because the some of the CIs do not overlap, the
observer 4 is clearly less precise than some other observers? 
Thankyou in advance for advice.
Lize van der Merwe 

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