SIGMA Transformation

SIGMA transformations are the same as used for OMEGA.

Untransformed 

SIGMA diagonals %RSE = (SE / Estimate) * 100 
where:
– SE is the standard error of the estimated parameter (SIGMA diagonal element)
– Estimate is the estimated value of the parameter (SIGMA diagonal element)

SIGMA off-diagonal elements are reported as Estimate(SE) 

sqrt(OM^2) 

SIGMA diagonals =  

SIGMA diagonal %RSE = (%RSE_{untransformed})/2 

SIGMA off-diagonals are reported as correlation(SE) 

sqrt(exp(OM^2) – 1) 

SIGMA diagonals =  

SIGMA diagonal %RSE =
exp(Estimate) / (2 * (exp(Estimate) – 1)) * Estimate * (%RSE_{untransformed}) 

SIGMA off-diagonals are reported as correlation(SE)