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When does change mean the same thing for everyone?
Measurement equivalence and developmental growth
Measurement validation · Growth modeling · Longitudinal analysis · SEM · Construct validity
When we observe differences in developmental or behavioral scores, how do we know they represent real differences in the underlying construct rather than differences in how the measurement performs?
Longitudinal research often assumes a score means the same thing across people and across time. Without that assumption, an apparent difference in a growth trajectory could reflect a change in the measurement rather than genuine development.
One project examined the measurement and developmental properties of the Early Communication Indicator, a standardized assessment of early communication development.
With a multidisciplinary team, I led analyses using parallel-process and piecewise latent growth models to examine developmental trajectories, relationships among communication domains, and transitions between communication strategies.
Why it matters — a measurement system should do more than assign a score. It should give confidence that observed change reflects the phenomenon we intend to understand: not only where someone is, but how they are changing.