Testing for Regime Switching

We analyze use of a quasi‐likelihood ratio statistic for a mixture model to test the null hypothesis of one regime versus the alternative of two regimes in a Markov regime‐switching context. This test exploits mixture properties implied by the regime‐switching process, but ignores certain implied serial correlation properties. When formulated in the natural way, the setting is nonstandard, involving nuisance parameters on the boundary of the parameter space, nuisance parameters identified only under the alternative, or approximations using derivatives higher than second order. We exploit recent advances by Andrews (2001) and contribute to the literature by extending the scope of mixture models, obtaining asymptotic null distributions different from those in the literature. We further provide critical values for popular models or bounds for tail probabilities that are useful in constructing conservative critical values for regime‐switching tests. We compare the size and power of our statistics to other useful tests for regime switching via Monte Carlo methods and find relatively good performance. We apply our methods to reexamine the classic cartel study of Porter (1983) and reaffirm Porter's findings.     

Relations between physical activity and behavioral and perceptual correlates among midwestern college students

OBJECTIVE: Given the inconsistent findings in the literature, the authors' purpose in this study was to examine the associations between physical activity and behavioral and perceptional correlates, such as binge drinking, cigarette smoking, fruit or vegetable consumption, and weight perceptions, among midwestern college students. PARTICIPANTS AND METHODS: The authors invited a convenience sample of 1,200 undergraduate college students enrolled in the 2004-2005 academic year in 4 different midwestern universities to participate in a survey. Of the 1,163 students who participated in the survey, a total of 1,134 usable surveys were received (response rate of 94.5%). RESULTS: Hierarchical multiple logistic regression analyses indicated that smoking, perceived weight, and consumption of fruit were independent predictors of physical activity when controlling for other variables. CONCLUSIONS: Physical activity promotion requires tailored approaches that are dependent on the target segment of the college student populations.     

Robust Confidence Regions for Incomplete Models

Call an economic model incomplete if it does not generate a probabilistic prediction even given knowledge of all parameter values. We propose a method of inference about unknown parameters for such models that is robust to heterogeneity and dependence of unknown form. The key is a Central Limit Theorem for belief functions; robust confidence regions are then constructed in a fashion paralleling the classical approach. Monte Carlo simulations support tractability of the method and demonstrate its enhanced robustness relative to existing methods.