In this paper we propose a test statistic to discriminate between models with nite variance and models with in nite variance. The test statistic is the ratio of the sample standard deviation and the sample interquartile range. Both asymptotic and nite sample properties of the test statistic are discussed. We show that the test has good power properties against in nite-variance distributions and...

Although the methodology for handling ordinal and dichotomous observed variables in structural equation models (SEMs) is developing rapidly, several important issues are unresolved. One of these is the optimal test statistic to apply as a test of overall model fit. We propose a new ‘‘vanishing tetrad’’ test statistic for such models. We build on Bollen’s (1990) simultaneous test statistic for t...

In this paper we propose a test statistic to discriminate between models with finite variance and models with infinite variance. The test statistic is the ratio of the sample standard deviation and the sample interquartile range. Both asymptotic and finite sample properties of the test statistic are discussed. We show that the test has good power properties against infinite-variance distributio...

| Fuzzy logic and fuzzy set theory provide an important framework for representing and managing impre-cision and uncertainty in medical expert systems, but the need remains to optimise such systems to enhance performance. This paper presents a general technique for optimizing fuzzy models in fuzzy expert systems by simulated annealing and N-dimensional hill climbing simplex method. The applicat...