Asymptotically distribution free (adf) interval estimation of coefficient alpha

Asymptotic distribution free (ADF) interval estimators for coefficient alpha were introduced in the context of an application by Yuan, Guarnaccia, and Hayslip (2003). Here, simulation studies were performed to investigate the behavior of ADF vs. normal theory (NT) interval estimators of coefficient alpha for tests composed of ordered categorical items under varied conditions of sample size, item skewness and kurtosis, number of items, and average inter-item correlation. NT intervals were found to be inaccurate when item skewness > 1 or kurtosis > 4.