Date of Award


Document Type


Degree Name



Quantitative Research Methods

First Advisor

Kathy E. Green, Ph.D.

Second Advisor

Duan Zhang, Ph.D.

Third Advisor

Bruce Uhrmacher

Fourth Advisor

Daniel Brisson

Fifth Advisor

Christopher Pretz


Disability rating scale, Functional independence Measure, Individual growth curve, Longitudinal analyses, Payer source, Traumatic brain injury


Using longitudinal data from the TBIMS ND, this study utilized a longitudinal hierarchical linear modeling approach to describe the effect of primary payer source on individual level change in outcomes including the FIM and DRS. To facilitate the use of parametric statistics, Rasch-transformed FIM and DRS scores were utilized; thus approaching an interval level of measurement. The FIM was separated into 3 separate cognitive, mobility, and self-care subscales. In this way, rehabilitation professionals including speech, physical, and occupational therapists for this TBI sample could reference results to inform current clinical practice.

Results indicated that FIM and DRS trajectories were best modelled using a negative exponential model. Significant variability was found in each growth parameter (Asymptote, Pseudo-Intercept, and Rate) (p < .05) for all unconditional models (FIM Cognitive, FIM Mobility, FIM Self-Care, and DRS). Reduced conditional models for the FIM Cognitive, FIM Mobility, FIM Self-Care, and DRS outcome variables were constructed including only covariates that related significantly to the growth parameters. Conditional model results showed that as a group, the functional status of individuals measured by the FIM and DRS outcomes in the TBIMS ND improved rapidly and then plateaued as a result of floor and ceiling effects. Characteristics such as age, education, employment, length or rehab stay, marital status, PTA, race, and sex were found to impact baseline FIM and DRS scores and the rate and extent of improvement over time. More importantly, and a primary focus of this study was the effect of payer source on FIM and DRS outcomes.

At the individual and group level, primary payer source was significantly related to the growth parameters for each FIM and DRS outcome. The strong association found between primary payer and the growth parameters suggested that initial successful rehabilitation outcomes were a function of the type of rehabilitation received and dependent on the payment source for services. These findings are especially important to rehabilitation clinicians. Clinicians can use this information to secure further funding and care resources from third party payers that will advance an individual's course in successful functional outcomes and quality of life over their lifetime.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.


Received from ProQuest

Rights holder

Melissa Carole Hofmann

File size

175 p.

File format





Statistics, Health Sciences