Comparison of three estimators of the number of species

We consider estimation of the number of cells in a multinomial distribution. This is one version of the species problem: there are many applications, such as the estimation of the number of unobserved species of animals; estimation of vocabulary size, etc. We describe the results of a simulation comparison of three principal frequent-ist' procedures for estimating the number of cells (or species). The first procedure postulates a functional form for the cell probabilities; the second procedure approxi mates the distribution of the probabilities by a parametric probability density function; and the third procedure is based on an estimate of the sample coverage, i.e. the sum of the probabilities of the observed cells. Among the procedures studied, we find that the third (non-parametric) method is globally preferable; the second (functional parametric) method cannot be recommended; and that, when based on the inverse Gaussian density, the first method is competitive in some cases with the third method. We also discuss Sichel's recent generalized inverse Gaussian-based procedure which, with some refine ment, promises to perform at least as well as the non-parametric method in all cases.     

HIV-infected woman. Illness cognition assessment.

1. Special attention is particularly important in addressing the mental health needs of HIV-infected women. These needs may involve issues such as concerns about present or future pregnancy; child-rearing, often as single parents; poverty, illicit drug use or addiction; and the potential lack of support services. 2. Diagnosis of HIV infection in women may be overlooked, as the clinical signs that routinely trigger the suspicion of HIV illness in men are often interpreted to reflect depression or psychological factors, such as stress or overwork, rather than raise the suspicion of HIV infection in women. 3. Understanding a woman's illness cognition is an important component of designing strategies that can enhance coping. The picture a woman generates regarding her illness is a composite of her experiences and responses, and determines to a large extent what she will do in response to her illness.     

Implications of temporal aggregation on the relation between two time series

Using a simple theoretical model and giving an empirical example it is investigated if it matters whether we use (monthly) averages or end-of-period (month) data in performing Granger-causality tests. It is shown that no major problems are to be expected if the two series are temporally aggregated in the same way, but non-trivial problems can occur if the two series have different kinds of temporal aggregation.     

The effect of 1980s tort reform legislation on general liability and medical malpractice insurance

A large number of states adopted tort reforms in the mid-1980s to limit the dramatic surge in insurance losses and premiums. Evidence based on liability insurance data by state indicates that these reforms substantially influenced general liability insurance. The levels of losses, premiums, and loss ratios (a measure of insurance profitability) all reflected the impact of the reforms. The large-scale reform efforts in 1986 were particularly influential. Medical malpractice insurance was much less sensitive to the reform efforts.     

Knowledge,power, and ethics in qualitative social research

Philadelphia, then and still one of the worst governed of America’s badly governed cities, was having one of its periodic spasms of reform. A thorough study of causes was called for. Not but what the underlining cause was evident to most white Philadelphians: the corrupt semi-criminal vote of the Negro Seventh Ward…. Would it not be well, to elucidate the known causes by a scientific investigation?… With my bride of three months, I settled in one room over a cafeteria run by a College Settlement, in the worst part of the Seventh Ward. We lived there a year, in the midst of an atmosphere of dirt, drunkenness, poverty and crime. Murder sat on our doorstep, police were our government, and philanthropy dropped in with periodic advice. (DuBois, 1968/1975: 194–5 also in Logan, ed. 1944: 42) What had been borne into me during my book studies was my utter ignorance of the manual-working class, that is, of four-fifths of my countrymen…. How was I to get an opportunity of watching, day by day, in their homes and in their workshops, a sufficient number of normal manual-working families to enable me to visualize the class as a whole; to understand what was meant by chronic poverty and insecurity of livelihood. (Webb, 1926: 146–7)     

城市可持续发展中的文化指标

本文为第三届“文化与城市可持续发展”国际会议的主题发言。本文介绍了会议背景 ,论述了文化及其与可持续发展的关系 ,都市化进程及其发展方向等问题 ,并着重阐述了本次会议的主题即“城市可持续发展中的文化指标” ,确立了本次会议的总体基调和基本政策     

Determinants of housing quality: A comparison of white,African-American,and Hispanic single-parent women

This study examines housing quality among three groups of single-parent women: white, African-American, and Hispanic. Three indicators of housing quality—crowding, affordability, and satisfaction—are used to discover the extent to which these groups experience housing problems. This study also explores differences and similarities in the factors that precipitate problems in housing quality for these three groups of single parents. Findings suggest important differences and similarities in the nature of housing quality problems among white, African-American, and Hispanic single-parent women. The specified variables explained about 20% of the variance in crowding, housing affordability, and housing satisfaction. On measures of objective and subjective housing quality, white single mothers are better housed than their African-American or Hispanic counterparts. Hispanic single mothers have the largest housing cost burden and average more persons per household than the other groups. African-Americans are twice as likely as either group to live in low-quality housing and reported the lowest average satisfaction with their housing. Her research interests include housing and neighborhood assessment and women and public policy issues. She has recently published articles inUrban Affairs Quarterly andHousing and Society on housing and neighborhood assessment criteria among black urban households and the housing cost burden of various groups of female-headed households. She received her Ph.D. from Ohio State University. Her research interests include the housing adjustment behavior of women and public policy. She has recently completed her thesis on the role of noncustodial parents in determining the quality of life of their children. She is also the recipient of the Tessie Agan Award for research excellence from the American Association of Housing Educators for a paper titled “Unterstanding Constraints and Residential Satisfaction among Low-Income Single-Parent Families.”