损失模拟模型的模拟与检验

为帮助精算师在不同的数据环境下选择最优的准备金评估方法,美国非寿险精算师协会组织开发了一个产生模拟索赔数据的开源软件系统——损失模拟模型,然而损失模拟模型是否能够按指定参数要求产生模拟数据需要进行检验.文章采用不同的参数估计方法和拟合优度检验方法对模拟索赔次数的分布、索赔额的趋势以及不同险种索赔次数之间的相关结构进行了统计检验,结果表明损失模拟模型对索赔次数的分布、索赔额的趋势能够产生一致的模拟,而对索赔次数数据之间相关结构的模拟存在不稳定性.     

A socio-ecological perspective of urban green networks: the Stockholm case

Landscape fragmentation threatens habitats, biodiversity and other ecosystem services. In tackling this threat, the dynamic processes of social-ecological systems should be recognised and understood. Although network analysis based on graph theory has been recognised as an efficient way of spatially understanding landscape or habitat connectivity, only few studies have offered specific approaches or suggestions for integrating detailed social-ecological values into geographical distributions. As a contribution to bridging this gap, this paper introduces a social-ecological network model for the issue of landscape or habitat fragmentation applied to the case of Stockholm, Sweden. Graph theory was used in combination with sociotope and biotope maps for simple visualisation of network situations in two-dimensional maps. The European crested tit (Lophophanes cristatus), European common toad (Bufo bufo) and human beings were selected as indicator species, based on a landscape ecology analysis in Stockholm Municipality in 2009. Slope, land use and human disturbance maps were assessed in order to decide cost values of travelling from node to node. Lease-cost-path accumulation was used to create ideal reference maps of green networks. Three separate maps were then developed for suggesting efficient routes for three indicators in city scale that mainly connect from the Royal National City Park to the other parts of the city. The model in Hjorthagen neighbourhood to highlight two practical paths that link this fragmented community to its neighbouring park areas. Findings make it possible to address two scales of network improvement strategies, namely first for the city-scale green network that connects geographical habitats (nodes) and the regional green wedges of the city, and the second that of neighbourhood links between habitats in detailed layers of green networks. Strategic improvement potentials are presented based on ideal reference maps of green networks correspondingly.     

Salat-al-Juma: organizing the public in Tahrir Square

What were the sources of solidarity that bound anti-government protesters in Tahrir Square? This article complicates Judith Butler’s claim that this solidarity originated in shared vulnerability to police violence and the practices of mutual care that were necessary to sustain bodies in the square. I draw on existing scholarship that suggests that passive knowledge of this shared vulnerability was already present among Egyptians, especially those working in the informal economy and living more of their lives – eating, chatting, praying, selling, etc. – on the streets of Egypt’s cities and thereby drawn into increasing contact with state police forces. Given that aggressive policing and intimidation had generated a sense of passive solidarity among Egyptians, I ask how this solidarity was transformed into animated opposition to the regime. My answer is that the Islamic congregational prayers as well as the Sunday Masses held during the revolution were spectacles of interfaith cooperation that inspired courage and trust across sectarian and religious/secular communities. These prayers were rational rituals that generated trust among diverse Egyptians that Mubarak had sown suspicion among and played against one another to stay in power. These were embodied rituals that lent moral support to more the mundane aspects of occupying Tahrir Square, which was symbolically and strategically important in bringing down the regime.     

Merging data from multiple sources: pretest and shrinkage perspectives

In this article, we have developed asymptotic theory for the simultaneous estimation of the k means of arbitrary populations under the common mean hypothesis and further assuming that corresponding population variances are unknown and unequal. The unrestricted estimator, the Graybill-Deal-type restricted estimator, the preliminary test, and the Stein-type shrinkage estimators are suggested. A large sample test statistic is also proposed as a pretest for testing the common mean hypothesis. Under the sequence of local alternatives and squared error loss, we have compared the asymptotic properties of the estimators by means of asymptotic distributional quadratic bias and risk. Comprehensive Monte-Carlo simulation experiments were conducted to study the relative risk performance of the estimators with reference to the unrestricted estimator in finite samples. Two real-data examples are also furnished to illustrate the application of the suggested estimation strategies.     

A new generalized two-sided class of distributions with an emphasis on two-sided generalized normal distribution

The ordinary-G class of distributions is defined to have the cumulative distribution function (cdf) as the value of the cdf of the ordinary distribution F whose range is the unit interval at G, that is, F(G), and it generalizes the ordinary distribution. In this work, we consider the standard two-sided power distribution to define other classes like the beta-G and the Kumaraswamy-G classes. We extend the idea of two-sidedness to other ordinary distributions like normal. After studying the basic properties of the new class in general setting, we consider the two-sided generalized normal distribution with maximum likelihood estimation procedure.     

The McDonald Gompertz distribution: Properties and applications

This article introduces a five-parameter lifetime model called the McDonald Gompertz (McG) distribution to extend the Gompertz, generalized Gompertz, generalized exponential, beta Gompertz, and Kumaraswamy Gompertz distributions among several other models. The hazard function of new distribution can be increasing, decreasing, upside-down bathtub, and bathtub shaped. We obtain several properties of the McG distribution including moments, entropies, quantile, and generating functions. We provide the density function of the order statistics and their moments. The parameter estimation is based on the usual maximum likelihood approach. We also provide the observed information matrix and discuss inferences issues. The flexibility and usefulness of the new distribution are illustrated by means of application to two real datasets.     

Evaluating modified generalized information criterion in presence of multicollinearity

When there are many explanatory variables in the regression model, there is a chance that some of these are intercorrelated. This is where the problem of multicollinearity creeps in due to which precision and accuracy of the coefficients is marred, and the quest to find the best model becomes tedious. To tackle such a situation, Model selection criteria are applied for selecting the best model that fits the data. Current study focuses on the evaluation of the four unmodified and four modified versions of generalized information criteria—Akaike Information Criterion, Schwarz's Bayes Information Criteria, Hannan-Quinn Information Criterion, and Akaike Information Criterion corrected for small samples. A simulation study using SAS software was carried out in order to compare the unmodified and modified versions of the generalized information criteria and to discover the best version amongst the four modified model selection criteria, for identifying the best model, when the collinearity assumption is violated. For the proposed simulation, two samples of size 50 and 100, for three explanatory variables X₁, X₂, and X₃, are drawn from Normal distribution. Two situations of collinearity violations between X₁ and X₂ are looked into, first when ρ = 0.6 and second when ρ = 0.8. The outcomes of the simulations are displayed in the tables along with visual representations. The results revealed that modified versions of the generalized information criteria are more sensitive in identifying models marred with high multicollinearity as compared to the unmodified generalized information criteria.     

Patterns and severity of menopausal symptoms among Jordanian women

We examined 359 women aged 45–65 years who visited Jordan University Hospital between February and November 2014. The menopausal symptoms were assessed using a validated Arabic version of the menopause rating scale. The mean age at menopause was 49.4 years. Women aged 50–55 years more frequently exhibited hot flushes and vaginal dryness. Although premenopausal women were 1.5 times more likely to experience irritability, perimenopausal women were more likely to experience hot flushes, physical and mental irritability, sexual problems, vaginal dryness, and joint and muscular discomfort. Hence, health care providers should focus on women at all stages of life.     

Underneath we’re angry: feminism and media politics in Britain in the late 1970s and early 1980s

In the late 1970s, a billboard advertisement for Gigi underwear was installed at street level in various British cities. It depicted a woman in a trench coat walking on the street at night and looking defiantly at the camera. A second image portrays her unbuttoning her coat and revealing her underwear. A caption reads “Underneath they’re all Lovable.” This billboard evoked a wave of feminist opposition exemplified by Rosalind Coward’s essay “Underneath we’re angry” attacking the Gigi advertisement for being an invitation to rape women as well as photographic works by The Polysnappers condemning the ad. This article contextualizes the passionate resistance to the Gigi advert within the time’s feminist debates, which characterized media images as oppressive towards women, the discourse around the ideological functioning of advertisements, debates on “the sexual politics of representation,” the political role of photography, social historical events, and the political significance of the street.