Multivariate Tests of Mean-Variance Efficiency and Spanning With a Large Number of Assets and Time-Varying Covariances

We develop a finite-sample procedure to test the mean-variance efficiency and spanning hypotheses, without imposing any parametric assumptions on the distribution of model disturbances. In so doing, we provide an exact distribution-free method to test uniform linear restrictions in multivariate linear regression models. The framework allows for unknown forms of nonnormalities as well as time-varying conditional variances and covariances among the model disturbances. We derive exact bounds on the null distribution of joint F statistics to deal with the presence of nuisance parameters, and we show how to implement the resulting generalized nonparametric bounds tests with Monte Carlo resampling techniques. In sharp contrast to the usual tests that are not even computable when the number of test assets is too large, the power of the proposed test procedure potentially increases along both the time and cross-sectional dimensions.     

An Empirical Analysis of Life Jacket Effectiveness in Recreational Boating

This article gives a measure of life jacket (LJ) effectiveness in U.S. recreational boating. Using the U.S. Coast Guard's Boating Accident Report Database from 2008 to 2011, we find that LJ wear is one of the most important determinants influencing the number of recreational boating fatalities, together with the number of vessels involved, and the type and engine of the vessel(s). We estimate a decrease in the number of deceased per vessel of about 80% when the operator wears their LJs compared to when they do not. The odds of dying are 86% higher than average if the accident involves a canoe or kayak, but 80% lower than average when more than one vessel is involved in the accident and 34% lower than average when the operator involved in the accident has more than 100 hours of boating experience. Interestingly, we find that LJ effectiveness decreases significantly as the length of the boat increases and decreases slightly as water temperature increases. However, it increases slightly as the operator's age increases. We find that between 2008 and 2011, an LJ regulation that requires all operators to wear their LJs—representing a 20% increase in wear rate—would have saved 1,721 (out of 3,047) boaters or 1,234 out of 2,185 drowning victims. The same policy restricted to boats 16–30 feet in length would have saved approximately 778 victims. Finally, we find that such a policy would reduce the percentage of drowning victims compared to other causes of death.     

The Effect of Poverty on Depression Among Turkish Children

Child and Adolescent Social Work Journal - This study was conducted to determine the effect of poverty on depression among Turkish children. The data of the study were collected in 2019 by using a...     

The effect of urinary incontinence on sexual functioning in turkish women of reproductive and menopausal ages

Objectives: The primary objective was to investigate the effects of urinary incontinence (UI) on Turkish women's sexual functioning. Methods: We evaluated 396 women and divided them into 4 groups: reproductive-aged women without UI (Group A), reproductive-aged women with UI (Group B), menopausal-aged women without UI (Group C), and menopausal-aged women with UI (Group D). Results: The mean Female Sexual Function Index (FSFI) score was significantly higher and the Beck's Depression Inventory scores were significantly lower in Group A. FSFI scores showed a strong negative correlation with age and parity and a strong positive correlation with years of education. Conclusions: Our findings suggest that UI is an independent risk factor for female sexual problems.     

Correspondence analysis of repair data: a case study for electric cable shovels

In mining operation, effective maintenance scheduling is very important because of its effect on the performance of equipment and production costs. Classifying equipment on the basis of repair durations is considered one of the essential works to schedule maintenance activities effectively. In this study, repair data of electric cable shovels used in the Western Coal Company, Turkey, has been analyzed using correspondence analysis to classify shovels in terms of repair durations. Correspondence analysis, particularly helpful in analysing cross-tabular data in the form of numerical frequencies, has provided a graphical display that permitted more rapid interpretation and understanding of the repair data. The results indicated that there are five groups of shovels according to their repair duration. Especially, shovels numbered 2, 3, 7, 10 and 11 required a repair duration of<1 h and maintained relatively good service condition when compared with others. Thus, priority might be given to repair them in maintenance job scheduling even if there is another failed shovel waiting to be serviced. This type of information will help mine managers to increase the number of available shovels in operation.