Case-control studies are subject to the problem of population stratification, which can occur in ethnically mixed populations and can lead to significant associations being detected at loci that have nothing to do with disease. Here, we describe a way to measure and correct for stratification by genotyping a moderate number of unlinked genetic markers in the same set of cases and controls in wh...

This paper surveys some recent work which seeks to model persistent income inequality and explain such phenomena as ghetto formation and poverty traps. The paper illustrates how a number of these models possess a common structure in which local spillover effects interact with income-based stratification of neighborhoods to transmit parental economic status from generation to generation. As such...

This is a continuation of a paper in which the role of types in semantic theory was explored. Inevitably, in that paper some issues in type theory and semantics were treated only in passing. In particular, little was said about Stratified Type Theories. This paper concentrates on these theories and provides a theoretical framework for semantic applications.

Stratification is one of the most widely used techniques in finite population sampling. Strata are disjoint subdivisions of a population, the union of which exhaust the universe, each of which contains a portion of the sample. Two of its essential statistical purposes are to: (1) allow for efficient estimation, especially in the case of stratification by size, and (2) deal statistically with su...

In this manuscript, we discuss the problem of determining the optimum stratification of a study (or main) variable based on the auxiliary variable that follows a uniform distribution. If the stratification of survey variable is made using the auxiliary variable it may lead to substantial gains in precision of the estimates. This problem is formulated as a Nonlinear Programming Problem (NLPP), w...