MTO Colloquium
Tuesday, October 6, PZ 45 at 12:45h
by dr. Mijke Rhemtulla
(University of Amsterdam)
‘The use of item parcels in structural equation modeling’
Structural equation modellers often reduce large sets of items (e.g.,
32 items on a subjective well-being questionnaire) into a smaller set of
subscale scores (e.g., 4 sum scores, each representing the sum of 8 items)
before building a structural equation model. This practice of “parceling”
is commonly used to reduce the complexity of a model, improve model
fit, and improve the distributional properties of observed variables. It is
also a highly contentious practice among methodologists, many of whom
note that parceling can substantially change both parameter estimates and
the substantive interpretation of latent variables.
In this talk, I will give the conceptual and mathematical basis of
parceling, describe some parcel-formation strategies that have been
proposed, discuss some of the arguments that have been levied for and
against the use of parcels, and present some analytic investigations into
the consequences of parceling at the population level. In particular, I’ll
consider the effects of parceling on the accuracy of parameter estimates,
model fit, and power to detect misspecifications in the measurement and
structural parts of a model.