nonbinROC: Software for Evaluating Diagnostic Accuracies with Non-Binary Gold Standards

ROC analysis is a standard method for estimating and comparing diagnostic tests' accuracies when the gold standard is binary. However, there are many situations when the gold standard is not binary. In these situations, traditional ROC methods applied have lead to biased and uninformative outcomes. This article introduces nonbinROC, software for R that implements nonparametric estimators proposed by Obuchowski (2005) for estimating and comparing diagnostic tests' accuracies when the gold standard is measured on a continuous, ordinal or nominal scale. The results produced from these estimators are interpreted in the same manner as in ROC analysis but are not associated with any ROC curve.

Economic mobility in Vietnam in the 1990s

Vietnam's high economic growth in the 1990s led to sharp reductions in poverty, yet over the same time period inequality increased. This increased inequality may be less worrisome if Vietnamese households experience a high degree of income mobility over time. This is because high mobility implies that the long-run distribution of income is more equally distributed than the short-run distribution, since some individuals or households are poor in some years, while others are poor in other years. The authors examine economic mobility in Vietnam using recent household survey panel data. The problem of measurement error in the income variable, which exaggerates the degree of economic mobility, is directly addressed. Correcting for measurement error dramatically changes the results. At least one half of measured mobility is because of measurement error.Statistical&Mathematical Sciences,Roads&Highways,Economic Theory&Research,Housing&Human Habitats,Environmental Economics&Policies,Economic Theory&Research,Housing&Human Habitats,Statistical&Mathematical Sciences,Inequality,Governance Indicators

Infantile mortality and fertility decisions in a stochastic environment

We analyze the effect of stochastic survival of children on fertility decision in a dynastic utility model where saving, so to speak, can only be made through having children, the number of which is an endogenous decision to the household. In our stochastic framework where the rate of population change undergoes a process of Brownian motion, the probability distribution of the steady state is well determined, and saving via the number of offsprings incorporates a precautionary component. Any health care assistance proposed to reduce the variance of the Brownian process, for example, to reduce the risk of premature infantile mortality, would have a negative effect on the fertility rate and a positive effect on the per capita consumption in the long run.Brownian motion

Hidden Markov Model Identifiability via Tensors

The prevalence of hidden Markov models (HMMs) in various applications of statistical signal processing and communications is a testament to the power and flexibility of the model. In this paper, we link the identifiability problem with tensor decomposition, in particular, the Canonical Polyadic decomposition. Using recent results in deriving uniqueness conditions for tensor decomposition, we are able to provide a necessary and sufficient condition for the identification of the parameters of discrete time finite alphabet HMMs. This result resolves a long standing open problem regarding the derivation of a necessary and sufficient condition for uniquely identifying an HMM. We then further extend recent preliminary work on the identification of HMMs with multiple observers by deriving necessary and sufficient conditions for identifiability in this setting.Comment: Accepted to ISIT 2013. 5 pages, no figure

An elementary proof of Euler formula using Cauchy's method

The use of Cauchy's method to prove Euler's well-known formula is an object of many controversies. The purpose of this paper is to prove that Cauchy's method applies for convex polyhedra and not only for them, but also for surfaces such as the torus, the projective plane, the Klein bottle and the pinched torus