The Profile run mode is only available for Population models. This option performs likelihood profiling to aid in understanding the effect of the fixed effect parameter estimates on the likelihood. This approach perturbs one of the selected fixed effects by an indicated amount or percentage and fixes (freezes) it while letting the other model parameters vary. On each perturbation, the model is fitted and its results are presented.
Select the fixed effect(s) to investigate by checking the Profiling box beside each fixed effect to include.
Enter comma-separated amounts or percentage values by which to perturb the parameter estimate in the Perturbations field.
Click Perturbations multiple times to toggle between Perturbations (%) and Perturbations (Amt).
If more than one parameter is selected, the profiling is done as many times as parameters are selected. Each parameter is perturbed by the indicated absolute amount or by a percentage of their estimate, and Phoenix will also display the original parameter estimate without perturbation. If a model is sensitive to a specific parameter, perturbing that parameter by a small amount will show a large effect on the likelihood.
For example, if the initial estimate of tvV is 10 and the perturbation values are entered as “–1, 1, 3", then the model is run four times with tvV frozen at 9, 10, 11, and 13. If the initial estimate of tvV is 10 and the perturbation percentages are “–10,10”, then the models are run with tvV frozen at 9, 10 and 11. A perturbation of zero is the default value and does not need to be entered.