Selecting the best one of several meifull populations

Consider k(k ≥ 2) two-parameter Meibull populations. Using type II censored data we want to select a best population. Me have proposed procedures which can be used for maximum likelihood estimators or simplified linear estimators of Che unknown parameters. The ranking of the populations is done by comparing their reliabilities at certain fixed time or by comparing their 2-eh quantiles. In selected cases, the constants needed for the procedures are tabulated using Monte Carlo methods.     

On multistage group screening designs

In this article we discuss multistage group screening in which group-factors contain differing number of factors. We describe a procedure for grouping the factors in the absence of concrete prior information, so that the relative testing cost is minimal. It Is shown that under quite general conditions, these designs will require fewer runs than the equivalent designs in which the group-factors contain same number of factors.     

On selecting populations better than a control: weibull populations case

Consider k( k ≥ 1) independent Weibull populations and a control population which is also Weibull. The problem of identifying which of these k populations are better than the control using shape parameter as a criterion is considered. We allow the possibility of making at most m(0 ≤ m < k) incorrect identifications of better populations. This allowance results in significant savings in sample size. Procedures based on simple linear unbiased estimators of the reciprocal of the shape parameters of these populations are proposed. These procedures can be used for both complete and Type II-censored samples. A related problem of confidence intervals for the ratio of ordered shape parameters is also considered. Monte Carlo simulations as well as both chi-square and normal approximations to the solutions are obtained.     

Some results on maximum likelihood estimators of parameters of exponential distribution under type I progressive censoring with changing failure rates

In this paper the study of relative bias (RB), exact variance and mean square error (MSE) of the maximum likelihood estimators of the exponential distribution under type I progressive censoring with changing failure rates is considered. A minimum mean square error (MMSE) estimator for the parameter at each stage is proposed. The numerical evalution of their relative performance is made for selected values of n and p. Further results concerning group-censoring, total expected waiting time and optimal spacings of the times of censoring are derived and results obtained by Kendell and Anderson (1971) are deduced as special cases.     

Interval estimation of the largest reliability of k weibull populations

A procedure is given for obtaining a random width confidence interval for the largest reliability of k Weibull populations. The procedure does not identify the populations for which the reliability would be a maximum. The maximum likelihood estimators or the simplified linear estimators of the reliability based on type II censored data are used. The cases considered include unknown shape parameters being equal or unequal. Simultaneous confidence intervals for the k reliabilities are also obtained. Tables for the lower and upper limits in selected cases are constructed using Monte Carlo methods.     

Reconfiguration graphs for vertex colourings of chordal and chordal bipartite graphs

A k-colouring of a graph G=(V,E) is a mapping c:V→{1,2,…,k} such that c(u)≠c(v) whenever uv is an edge. The reconfiguration graph of the k-colourings of G contains as its vertex set the k-colourings of G, and two colourings are joined by an edge if they differ in colour on just one vertex of G. We introduce a class of k-colourable graphs, which we call k-colour-dense graphs. We show that for each k-colour-dense graph G, the reconfiguration graph of the ?-colourings of G is connected and has diameter O(|V|²), for all ?≥k+1. We show that this graph class contains the k-colourable chordal graphs and that it contains all chordal bipartite graphs when k=2. Moreover, we prove that for each k≥2 there is a k-colourable chordal graph G whose reconfiguration graph of the (k+1)-colourings has diameter Θ(|V|²).     

Longing for Mourning

“Longing for Mourning” is a meditation on the verities of events that establish the ostensible stability of supposedly ordinary relationships—commitment, house-buying, and marriage. Influenced by the long history of meditations and commentarial literature on loss and aesthetics, this biographical essay is written as an aesthetic embodiment of theoretical positions. It ruminates on the forms through which time, death, loss, and repeated mourning transform such verities when they are the life story of an interracial, interclass, transcontinental and transnational relationship between two women.     

Characteristics of cocaine users in a private inpatient treatment setting.

Patient records were reviewed from an eighteen-month period of a private hospital adult addictive disease unit. Of 667 consecutive admissions, sixty-five (49 males, 16 females) were diagnosed with cocaine abuse or dependence; 38 percent were from rural areas. Although mean age of males and females was similar, males had a longer duration of use (8.2 years versus 5.8 years), however, females used an average of 14 grams per week versus 9.5 grams per week for males. African-American patients were over-represented among the cocaine using sample and also among the sample who chose smoking as their route of administration. A larger percentage of males had legal problems and admitted to "dealing," when compared to females. Those from rural areas were more likely to be married and less apt to have legal problems.     

Prevalence of snoring in college students

Snoring in college students may be the earliest presentation of adult sleep-disordered breathing, yet the literature contains few studies that demonstrate its effects on learning or whether early diagnosis leads to interruption of disease progression or prevention of comorbidities. OBJECTIVE AND PARTICIPANTS: The authors conducted this study in January-April 2004 to assess the prevalence of snoring in college students (N = 2,200). METHODS: They developed a questionnaire on sleep behaviors and distributed it to 18- to 25-year-old undergraduates at a California university. RESULTS: Almost one-third (30%) of participants reported snoring. The prevalence of snoring was higher among men than women (42% and 25%, respectively). The prevalence of self-reported snoring was highest in Asian students (37%). CONCLUSIONS: Snoring is highly prevalent in college students; prevalence is higher in men than women, correlates with body mass index, and varies by ethnicity.