The MxCI class has the following slots: rcl{
reference - The name of the object
lowerdelta - Either a matrix or a data frame
upperdelta - A vector for means, or NA if missing
}
The reference slot contains a character vector of named free parameters, MxMatrices and MxAlgebras on which confidence intervals are desired. Individual elements of MxMatrices and MxAlgebras may be listed as well, using the syntax matrix[row,col] (see Extract for more information).
The lowerdelta and upperdelta slots give the changes in likelihoods used to define the confidence interval. The upper bound of the likelihood-based confidence interval is estimated by increasing the parameter estimate, leaving all other parameters free, until the model -2 log likelihood increased by upperdelta. The lower bound of the confidence interval is estimated by decreasing the parameter estimate, leaving all other parameters free, until the model -2 log likelihood increased by lowerdata.
Likelihood-based confidence intervals may be specified by including one or more MxCI objects in an MxModel object. Estimation of confidence intervals requires model optimization using the mxRun function with the intervals argument set to TRUE. The calculation of likelihood-based confidence intervals can be computationally intensive, and may add a significant amount of time to model estimation when many confidence intervals are requested.