Explaining Undocumented Migration to the U.S.

Using data from the Mexican Migration Project and the Latin American Migration Project, we find that undocumented migration from Mexico reflects U.S. labor demand and access to migrant networks and is little affected by border enforcement, which instead sharply reduces the odds of return movement. Undocumented migration from Central America follows primarily from political violence associated with the U.S. intervention of the 1980s, and return migration has always been unlikely. Mass undocumented migration from Mexico appears to have ended because of demographic changes there, but undocumented migration from Central America can be expected to grow slowly through processes of family reunification.     

How do people perceive urban trees? Assessing likes and dislikes in relation to the trees of a city

Cities are systems that include natural and human-created components. When a city grows without proper planning, it tends to have low environmental quality. If improving environmental quality is intended, people’s opinion should be taken into account for a better acceptance of urban management decisions. In this study, we assessed people’s perception of trees by conducting a survey with a controlled sample of citizens from the city of Morelia (west-central Mexico). Citizens liked both native and exotic tree species and rejected mainly exotic ones. Preference for trees were related to tree attributes; such as size. Trees that dropped leaves or tended to fall were not liked. The most-mentioned tree-related benefits were oxygen supply and shade; the most mentioned tree-related damages were accidents and infrastructure damage. The majority of respondents preferred trees near houses to increase tree density. Also, most respondents preferred trees in green areas as well as close to their houses, as they consider that trees provide oxygen. The majority of the respondents thought more trees were needed in the city. In general, our results show that although people perceive that trees in urban areas can cause damages, they often show more interest for the benefits related to trees and consider there should be more trees in cities. We strongly suggest the development of studies that broaden our knowledge of citizen preferences in relation to urban vegetation, and that further policy making takes their perception into account when considering creating new urban green areas, regardless of their type or size.     

Four comments for the paper from Liu et al. (2019)

We give comments for the paper from Liu et al. (2019) about the Item Response Theory (IRT) model under consideration, the justification to compute Marginal likelihood, about what we learn with the data analysis performed and finally, about the computational issues in this paper.     

Acceptance Sampling Plans from Truncated Life Tests Based on the Generalized Birnbaum–Saunders Distribution

In this article, we develop acceptance sampling plans when the life test is truncated at a pre-fixed time. The minimum sample size necessary to ensure the specified median life is obtained by assuming that the lifetimes of the test units follow a generalized Birnbaum–Saunders distribution. The operating characteristic values of the sampling plans as well as producer's risk are presented. Two examples are also given to illustrate the procedure developed here, with one of them being based on a real data from software reliability.     

Some properties of the tukey g and h family of distributions

The g and h family of distributions, introduced by J.W. Tukey, is generated by a single transformation of the standard normal which allows for symmetry and heavier tails. Selected percentage points are tabulated, and a closed-form solution for the moments, when they exist, is found. A comparison is made with the Pearson system of distributions. The g and h distributions cover most of the Pearson family to an adequate approximation, when the first four moments exist, and also generate a variety of other types of distributions. Selected distributions graphically illustrate the great variety of possible shapes.     

Use of bayesian analysis to design of clinical trials with one treatment

Assuming a Weibull distribution, the posterior distribution for the median survival time is derived in the presence of arbitrary right censorship. In the design of clinical triaLs, suppose k follow-up periods have been completed and it is desired to plan the follow-up period k+1. In this context, criteria are presented that can be employed in determining the number of new patients to be enrolled in the follow-up period k+1.     

Constant hazard against a change-point alternative: a bayesian approach with censored data

A Bayesian approach to the problem of a constant hazard with a single change-point is developed using noninformative reference priors. We also present a generalization for the comparison for two treatments.