Multi-risk Model Research Articles

Precise Large Deviations for the Actual Aggregate Loss Process

In this article, we propose a customer-arrival-based insurance risk model, in which customer's actual claim sizes are described as i.i.d. heavy-tailed r.v.'s multiplied with a generalized shot function, and the model can be treated as a generalized Poisson shot noise process. We obtain some precise large deviation results for the actual loss process and extend the results to the multi-risk model.

Maternal psychopathology and child risk factors in infantile anorexia

This study examines a transactional and multirisk model for Infantile Anorexia (IA) and investigates the contributions of the parent, the child, and dyadic interactional variables related to this feeding disorder. The sample consisted of 371 mother-child pairs (children aged 6-36 months), of which 187 pairs of mothers and normally developing children (ND-group), and 184 mothers and IA children. All dyads were videotaped during feeding; mothers completed questionnaires assessing their psychological profiles and eating attitudes, as well as their children's temperament and emotional/ behavioral functioning. Analyses revealed that the IA-group showed higher scores in symptomatic characteristics both of the mother and of the child, and dysfunctional interactions during feeding as compared with the ND-group. Further analyses revealed that both child and maternal characteristics are significant predictors of dyadic interactional conflict. Results confirm that a multidimensional assessment is critical in the evaluation of IA.

Early language development of children at familial risk of dyslexia: Speech perception and production

Speech perception and speech production were examined in 3-year-old Dutch children at familial risk of developing dyslexia. Their performance in speech sound categorisation and their production of words was compared to that of age-matched children with specific language impairment (SLI) and typically developing controls. We found that speech perception and production performance of children with SLI and children at familial risk of dyslexia was poorer than that of controls. The results of the at-risk and SLI-group were highly similar. Analysis of the individual data revealed that both groups contained subgroups with good and poorly performing children. Furthermore, their impaired expressive phonology seemed to be related to a deficit in speech perception. The findings indicate that both dyslexia and SLI can be explained by a multi-risk model which includes cognitive processes as well as genetic factors. Learning outcomes: As a result of reading this paper the reader will be able to (1) learn about the relationship between language and literacy; (2) recognise that dyslexia and specific language impairment may show similar areas of language difficulties, and (3) understand that both disorders can be interpreted within a multirisk model, including cognitive processes as well as genetic factors.

Precise Large Deviations for Sums of Random Variables with Consistently Varying Tails in Multi-Risk Models

Assume that there are k types of insurance contracts in an insurance company. The ith related claims are denoted by {X ij , j ≥ 1}, i = 1,…,k. In this paper we investigate large deviations for both partial sums S(k; n 1,…,n k ) = ∑ i=1 k ∑ j=1 n i X ij and random sums S(k; t) = ∑ i=1 k ∑ j=1 N i (t) X ij , where N i (t), i = 1,…,k, are counting processes for the claim number. The obtained results extend some related classical results.

Precise Large Deviations for Sums of Random Variables with Consistently Varying Tails in Multi-Risk Models

Assume that there are k types of insurance contracts in an insurance company. The ith related claims are denoted by {Xij, j ≥ 1}, i = 1,…,k. In this paper we investigate large deviations for both partial sums S(k; n1,…,nk) = ∑i=1k ∑j=1niXij and random sums S(k; t) = ∑i=1k ∑j=1Ni (t)Xij, where Ni(t), i = 1,…,k, are counting processes for the claim number. The obtained results extend some related classical results.

Quantifying the strength and durability of induced immunity to HIV infection in women engaging in unprotected sexual contacts with infected men

Evidence is accumulating that exposure to human immunodeficiency virus (HIV) can lead to an increased resistance or immunity to subsequent infection. A multirisk model that permits either induced immunity or infection to develop after heterosexual inoculation with HIV is shown to be compatible with a wide spectrum of disparate male-to-female transmission data. When the model is applied to time- dependent, HIV-seroprevalence data, the probability that an unexposed woman would remain unexposed after an unprotected contact with an infected man was estimated to be greater than 0.95 on the average. Thus, it would require at least 14 unprotected sexual contacts with HIV-infected men for 50% of an unexposed cohort of women to become exposed to the virus. This suggests that there is a low probability that HIV virions will be found to have penetrated the mucosal barriers of the reproductive tract after a contact. The model also predicts, that the average woman whose mucosal barriers have been breached by HIV has a significant probability of developing immunity to the virus rather than infection. Modelling data for a cohort of unexposed Nairobi women leads to the prediction that the probability of acquiring induced immunity per contact is about 60% of the probability of acquiring the disease per contact. The modelling results also predict that those who had developed resistance to HIV run the small, but significant risk of becoming infected nonetheless by continuing high-risk behavior. For the common contact rate of ten per month, the modelling predicts that the HIV-transmission risk per contact for unexposed women in the Nairobi cohort is 1 178 while the transmission risk for the cohort's immunized women is 1 1548 . These numbers suggest that HIV infection is difficult to transmit through heterosexual intercourse on the average and that male-to-female HIV-transmission risk per contact for African women lies between 1 178 and 1 1548 . Direct confirmation of the predictions in the last paragraph has been subsequently observed in two completely independent studies. The Nairobi research team recently reported that a notable number of Nairobi prostitutes previously identified to be members of the HIV-resistant group became infected nonetheless. Second, in a study of 174 sexually monogamous, discordant couples in Rakai, Uganda reporting contacts rates of nine to ten per month, the male-to-female HIV-transmission risk per contact was found to be 1 769 by direct measurement, a value that falls between the above limits of 1 178 and 1 1548 predicted by the modelling. Thus, a second major prediction of this paper has been directly confirmed, and induced immunity to HIV is limited and not absolutely protective. Circumstantial evidence suggests that the induced immunity to HIV predicted by the model could be generated and/or initiated by nonspecific innate immune responses, specific immunological responses, including IgA-mediated mucosal immunity and cytotoxic T lymphocytes (CTL) immunity, or some combination of the above. It is suggested here, that a decrease in the ability of HIV virions to penetrate the protective mucus layer of the reproductive tract may be a prerequisite, cofactor, or the principle cause of the induced immunity or resistance demonstrated to exist in this paper. The value of the probability that induced immunity to HIV will develop after a contact is shown to be a sensitive function of the woman's human leucocyte antigen (HLA) supertype profile.

Child sexual abuse, peer sexual abuse, and sexual assault in adulthood: a multi-risk model of revictimization.

This study explored the predictors and consequences of sexual assault occurring after the age of 16 years in a nonclinical sample of women. Child sexual abuse occurring before the age of 16 years was the only predictor of later sexual assault among comorbid risk factors. Peer sexual abuse, number of perpetrators, age at time of sexual abuse, and severity of sexual abuse did not increase the risk for later sexual assault. Adult sexual assault victims showed lower levels of mental health functioning than did survivors of child or peer sexual abuse. We discuss a specificity model of revictimization and the differential effects of child, peer, and adult sexual trauma on the developmental trajectory of sexual violence and psychosocial functioning.

Global Asset Allocation with Multirisk Considerations

Multirisk asset allocations help investors optimally balance their desire for expected return with their aversion to two types of risk—absolute volatility and tracking error relative to a benchmark. Zhang empirically tests a multirisk optimization model by allocating funds among global equity markets. The results suggest that mean– variance tracking error optimization may provide more efficient portfolios than the traditional approach of mean–variance with constraints.

Preventive intervention approaches in infancy

In view of the actual condition of the insurance company, a multi-risk model is proposed. The lower and upper bounds for the sums of subexponential claims in this model are given. The proof method is based on the results of the total claim amount under subexponential class.

Maximum Likelihood Estimation For Multi-Risk Model

In this paper we discuss a probabilistic model of failure due to competing causes of failure operating on a unit during its lifetime. Following Cox we term this the Multi-Risk Model. We impose some well-known parametric forms on the underlying distributions of the model and obtain maximum likelihood estimates for the parameters of the distributions. The asymptotic variance-covariance matrix of the estimates is derived. We give examples using the exponential and Weibull distributions. The theory is applied to data published by Mendenhall and Hader, who studied a Single-Risk Model.