Webinar Title
The Role of Person Ability Scores in Standardized Testing of Individuals with Intellectual and Developmental Disabilities (1.5 CE/CPD)
Date and Time
Thursday, October 22, 2026
11:30 am – 1:00 pm CDT
Abstract
The serial assessment of development in individuals with intellectual and developmental disabilities (IDD) informs medical and therapeutic decision-making. While the norm-referenced scores produced by standardized tests are well-suited to the diagnostic context, they have serious limitations when used for monitoring. Alternative methods for operationalizing performance must be considered, especially when an individual’s performance falls below the normative floor. Many tests produce person ability scores, which come from the Rasch analysis or Item Response Theory methodology commonly used in the test development process, and are ideally suited to the monitoring of within-person change. In this intermediate-level webinar, the speaker will describe the derivation of person ability scores and will review the psychometric case for their use in monitoring individuals with IDD. Suggested guidelines for the integration of person ability scores into clinical practice will be provided.
Learning Objectives
Following this webinar, attendees will be able to:
- Describe limitations in the use of norm-referenced scores for monitoring change in individuals with IDD.
- Identify the appropriate conditions for use of person ability scores.
- Accurately interpret the meaning of person ability scores.
Bio
Cristan Farmer, PhD, is a senior staff scientist in the Rosamund Stone Zander and Hansjoerg Wyss Translational Neuroscience Center at Boston Children’s Hospital. She is a research psychologist and statistician with expertise in intellectual and developmental disabilities and clinical trials. Her research interests are focused on the psychometric and statistical challenges of clinical trials in rare diseases affecting neurodevelopment.