Ordinary least squares and Stein-rule predictions in regression models under inclusion of some superfluous variables

This article considers a misspecified linear regression model in which misspecification relates to the inclusion of some explanatory variables. Assuming the distribution of disturbances to be not necessarily normal, this paper investigates the efficiency properties of predictions arising from ordinary least squares and Stein-rule when the aim is to predict either the actual value or the mean value of the study variable.     

Diabetes Vis-a-vis Mind and Body

Health as defined by World Health Organization (WHO) is not onlyfreedom from disease but also normal physical and psychological well being.Metabolic diseases are becoming more common due to our faculty life styleand adjustment to very fast changing environments and demands. Diabetesis one of them. Currently up to 10 percent of Indian's urban population and2 percent of rural population above the age of 15 have diabetes. An earlierWHO report had noted that it is no longer considered a disease of affluence,given the changing life styles and diets of third world communities. Eventhe median age when an urban Indian is likely to develop diabetes is fallingalarmingly, with men and women in their mid 30's and early 40's showingfull blown symptoms of a type diabetes that usually occurs only much later.     

Operational research in Indian defence

The paper gives an outline of the areas of Operational Research (OR) where work in the Defence Department in India has been successful, even though it has not been fully implemented due to certain reservations on the part of the users and some limitations of OR scientists. There is an ad hoc quality in the decision making of the customer, and no large scale OR models are available which give a total effect of defence spending on social measures and human resources development. OR would be able to contribute to a balanced spending on defence in developing countries, if effort were made to analyse defence problems in the wider context. The author was formerly Director of Scientific Evaluation, Ministry of Defence, India.     

Mathematical models and their applications in medicine and health

Mathematical models have great potentialities as regards their utility in different disciplines of medicine and health. This paper attempts to elucidate their uses in the field. A brief mention of some models has also been made. Mathematical models are useful in epidemiologic research, planning and evaluation of preventive and control programmes, clinical trials, measurement of health, cost-benefit analysis, diagnosis of patients and in maximizing effectiveness of operations aimed at attaining specified goals within existing resources.     

Maximum likelihood estimation for the proportional odds model with mixed interval-censored failure time data

This article discusses regression analysis of mixed interval-censored failure time data. Such data frequently occur across a variety of settings, including clinical trials, epidemiologic investigations, and many other biomedical studies with a follow-up component. For example, mixed failure times are commonly found in the two largest studies of long-term survivorship after childhood cancer, the datasets that motivated this work. However, most existing methods for failure time data consider only right-censored or only interval-censored failure times, not the more general case where times may be mixed. Additionally, among regression models developed for mixed interval-censored failure times, the proportional hazards formulation is generally assumed. It is well-known that the proportional hazards model may be inappropriate in certain situations, and alternatives are needed to analyze mixed failure time data in such cases. To fill this need, we develop a maximum likelihood estimation procedure for the proportional odds regression model with mixed interval-censored data. We show that the resulting estimators are consistent and asymptotically Gaussian. An extensive simulation study is performed to assess the finite-sample properties of the method, and this investigation indicates that the proposed method works well for many practical situations. We then apply our approach to examine the impact of age at cranial radiation therapy on risk of growth hormone deficiency in long-term survivors of childhood cancer.     

Modeling cross-price effects on inter-category dynamics: The case of three computing platforms

Existing research on the market evolution model focused on new product sales growth for a single product category. Accordingly, this approach did not imply any interactions among separate but related product categories that could affect each other's market growth. However, the importance of analyzing these inter-category relationships is emphasized because such an analysis helps managers to better understand the underlying market dynamics and develop more profitable product-line strategies for a multi-product market.     

Sophisticated voting rules: the case of two tournaments

A voting rule maps voter preferences into outcomes, and is called sophisticated if there exists a voting tree whose sophisticated outcomes coincide with the voting rule for every voter preference. As yet, no complete characterization of such rules is available. In this paper, we provide an important step toward this characterization by completely solving the problem when there are two possible sets of voter preferences.The second author was supported by the Office of Naval Research, Grant N00014-92-J-1387.     

Estimating Incidence Rate on Current Status Data with Application to a Phase IV Cancer Trial

New drug discovery in the pediatrics has dramatically improved survival, but with long- term adverse events. This motivates the examination of adverse outcomes such as long-term toxicity in a phase IV trial. An ideal approach to monitor long-term toxicity is to systematically follow the survivors, which is generally not feasible. Instead, cross-sectional surveys are conducted in Hudson et al. (2007 Hudson , M. M. , Rai , S. N. , Nunez , C. , Merchant , T. E. , Marina , N. M. , Zalamea , N. , Cox , C. , Phipps , S. , Pompeu , R. , Rosenthal , D. ( 2007 ). Noninvasive evaluation of late anthracycline cardiac toxicity in childhood cancer survivors . J. Clin. Oncol. 25 : 3635 – 3643 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), with one of the objectives to estimate the cumulative incidence rates along with specific interest in fixed-term (5 or 10 year) rates. We present inference procedures based on current status data to our motivating example with very interesting findings.