The Parameters tab contains six sub-tabs that allow users to modify the structural parameters, specify values for the fixed and random effects, and add covariates.
Covariate effects can be specified in population modeling as well as in individual modeling, however, care must be taken not to over-parameterize the individual model. For example, suppose body weight W affects volume V. Then the model for V might be V=tvV+W*dVdW. In this case, if W is constant for the individual, the model is over-parameterized, because tvV and dVdW are redundant. However, if W is time-varying, the model is not over-parameterized. Covariates can also be useful if the data are pooled, or all subjects are modeled together.
Other covariates can be included in the individual model, even though they may not affect any structural parameters, because they may appear in secondary parameters, such as AUC.
Columns mapped as covariates (including categorical or occasion covariates) can only be numeric. The user can associate a label to the numeric categorical covariate, for example, and the label will be displayed in graphs even if the underlying data is numeric.
Structural sub-tab
Covar. Type sub-tab
Fixed Effects sub-tab
Random Effects sub-tab
Secondary sub-tab
Scenarios sub-tab
