Here - Tilburg University

Author and presenter
Kuijpers, Renske E.; Tilburg School of Social and Behavioral Sciences
Title
Testing Cronbach's Alpha Using Feldt's Approach and a New Marginal Modelling
Approach
Abstract
Feldt developed an approach for testing three relevant hypotheses
involving Cronbach's alpha: H01, alpha equals a particular criterion; H02, two
alpha coefficients computed on two independent samples are equal; and H03,
two alpha coefficients computed on the same sample are equal. The assumptions
of Feldt's approach are unrealistic for many test and questionnaire data, and
little is known about the robustness of the approach against violations of the
assumptions. We propose a new approach to testing the three hypotheses. The
new approach uses marginal modelling and is based on weaker assumptions.
The Type I error rate and the power of both approaches were compared in a
simulation study using realistic conditions. In general, the two approaches
showed similar results showing that Feldt's approach is robust against violations
of the assumptions. In some cases, however, the marginal modelling approach
was more accurate: For computing Type I error rates for very high values of
alpha, for computing Type I error rates for hypothesis H03, and for computing
the power of hypothesis H03 using a small sample size.