Characterization of Continuous Distributions by Variance Bound and Its Implications to Reliability Modeling and Catastrophe Theory

We generalize some of the existing results on characterization of continuous distributions by lower bound on the variance and point out their equivalence to characterization of life distributions by relationship between conditional expectation and failure (reversed failure) rate. It is shown that these lower bounds are the same as, Cramer–Rao bound in the regular case and improves upon the latter in the non-regular case. Some applications to reliability modeling and catastrophe theory are pointed out.     

On generalized hyper-Poisson distribution of order k and its application

ABSTRACT

Here we introduce a new class of distributions namely the generalized hyper-Poisson distribution of order k (GHPD(k)) as an order k version of the alpha-generalized hyper-Poisson distribution of Kumar and Nair (Statistica, 2014b Kumar, C.S., Nair, B.U. (2014b). A three parameter hyper-Poisson distribution and some of its properties. Statistica. 74(2):183–198. [Google Scholar]). Several properties of the GHPD(k) are derived and the estimation of the parameters of the distribution by the method of mixed moments and the method of maximum likelihood is discussed. Certain testing procedures are suggested and all these estimation and testing procedures are illustrated with the help of a real-life data set. Further a simulation study is conducted.     

Combining Judgmental and Statistical Forecasts: An Application to Earnings Forecasts

This study investigated the accuracy of combinations of statistical and judgmental forecasts of annual accounting earnings. Combined forecasts were generated as equally weighted (i.e., simple averages) and unequally weighted combinations of individual forecasts from time-series models of quarterly and annual earnings (statistical forecasts) and security analysts' forecasts of quarterly and annual earnings (judgmental forecasts). The effect of the number of individual forecasts combined on the accuracy of the combined forecasts was also examined. The empirical results indicated that, on the average, combined forecasts were more accurate than individual forecasts. The results also indicated that although analysts' forecasts are based on a wider information set, the accuracy of their forecasts could be improved by combining them with forecasts generated from statistical models. Even if the best individual forecast could be identified in advance, gains in accuracy could be achieved by using combinations of two other forecasting methods. Several of the combined forecasts were superior to the most accurate individual forecast. Forecasts combined by using unequal weights derived from a regression model proved more accurate than equally weighted combinations. Forecasting accuracy improved and the variability of accuracy across different combinations decreased as the number of forecasts in the combination increased.     

What Risks Are People Concerned About

An unusual questionnaire was used to explore what risks concern laypeople. It asked respondents to list, in their own words, as many risks of personal concern as they could. They then selected the five risks of greatest concern and answered a set of specific questions about each. A coding scheme was developed for categorizing these responses and was shown to have good reliability. The questionnaire was administered to a heterogeneous convenience sample of subjects. They reported a very broad range of risks of concern, which differed in plausible ways as a function of their gender and age. Females and student-age subjects were generally more concerned about the environment, whereas males and older subjects were more likely to mention health and safety risks. Both the extent of the risk-reduction actions that they reported and their expressed willingness to pay for future risk reductions were greater for risk that presented a direct personal threat (e.g., health risks) than for risks that posed a diffuse threat to the environment or to people in general (e.g., pollution). Respondents perceived themselves as bearing primary responsibility for managing threats to their own health, but generally saw government as bearing a heavier responsibility for managing environmental risks (especially for pollutants) and war. The questionnaire instrument and coding structure developed for this work are well-suited to a variety of future research applications. They provide a way to identify the risks that concern lay groups, as well as to track the evolution of those concerns over time.     

A generalized Pearson system useful in reliability analysis

In the present note, we study an extended class of Pearson system of distributions in the context of reliability. It is shown that the proposed class of models can be characterized by a relatioaship between the failure rate and the conditional moments. Further, we develop a procedure to identify an increasing (decreasing) failure rate model in the generalized Pearson system.     

India well prepared for meeting future goals

In India many of the past goals for reduction in birth rates have not been achieved for various reasons, and although contraceptive usage has increased it has not been sufficient to overtake the reduction in death rates. From 1971-80 about 1/2 of the population of the country was subject to a decline in growth rate, and the number of eligible couples using effective contraception was 10.6% in 1971 and 22.7% in 1981 in spite of an increase in the number of such couples. The death rate declined from 27.4 in 1941-51 to 14.8 in 1971-81 with a corresponding increase in life expectancy from 32-52 years. However the growth rate has reached a plateau during 1971-81. Since its inception the Family Welfare Program in India is estimated to have averted 49 million births including 5 million in 1981-82. Future goals are: 1) reduction in birth rate from 35 in 1981 to 21, death rate from 14 to 9 and infant mortality rate from 125 to 60 by the year 2000 along with reductions in maternal mortality and morbidity, and 2) an increase in the percentage of couples protected from 23.6 in 1982 to 60 in 2000, and 3) population size of 950 million by the year 2000 and the commencement of population stabilization leading to a population of about 1200 million by the middle of the 21st century. Future strategies for the promotion of planned parenthood include information, education, and communication programs, incentives and disincentives, involvement of nongovernmental agenices, provision of services and supplies, linkages with other sectors, and monitoring and evaluation activities. Emphasis will be put on interpersonal communication channels to promote the program as a mass movement.     

Quantile based stop-loss transform and its applications

Partial moments are extensively used in actuarial science for the analysis of risks. Since the first order partial moments provide the expected loss in a stop-loss treaty with infinite cover as a function of priority, it is referred as the stop-loss transform. In the present work, we discuss distributional and geometric properties of the first and second order partial moments defined in terms of quantile function. Relationships of the scaled stop-loss transform curve with the Lorenz, Gini, Bonferroni and Leinkuhler curves are developed.     

Characterization of continuous distributions by properties of conditional variance

In the present paper we study the properties of the left and right truncated variance of a function of a non-negative random variable, that characterize a class of continuous distributions. These properties include characterizations by the relationships the conditional variance has with the truncated expectations and/or the failure rate as well as the lower bound to the conditional variance. It is shown that the characteristic properties are linked to those based on the relationship between the conditional means and the failure rates, discussed in the literature. The lower bound developed here compares favourably with that given by the Cramer–Rao inequality.     

Developing a clinical trial governance framework for pharmaceutical industry-funded clinical trials

ABSTRACT

Rising concerns relating to pharmaceutical sponsor bias in the conduct of clinical trials have compelled the need to develop a clinical trial governance framework. This article describes the development of the Conflict of Interest in Research (COIR), a clinical trial governance framework. The COIR, consisting of three process phases (initiation, concurrent, and ongoing), developed following a needs assessment, using a four-stage methodology, and evaluated against the International Conference on Harmonization--Good Clinical Practice (ICH-GCP) guidelines. The Conflict of Interest Resolution algorithm, the backbone of COIR, enables constant surveillance to detect/resolve conflicts at all stages of the clinical trial life-cycle. COIR promotes interaction between the regulatory system and the sponsors, independent of individuals. COIR enables rapid detection of scientific and financial conflicts, to prevent subject harm and, to assure optimal funds utilization, the latter feature helped to reduce a significant burden for the ethics committee, as it lacks financial expertise. COIR is a semi-automated Oracle system, requires manpower, and is affected by human expertise and subjectivity. Complete automation to overcome this limitation will still need human expertise to scale changing trial regulations. Nevertheless, the COIR has won the distinction of the “most favored site” from pharmaceutical sponsors and is anticipated to be adopted by other clinical trial sites.     

Software reliability assessment using accelerated testing methods

The use of operational profiles and usage-based testing has received considerable attention recently in the software engineering literature. Testing under the actual operational profile can, however, be expensive, time consuming or even infeasible in situations where the performance of a system is dominated by infrequent but highly critical events. We consider a real application that deals with telecommunications network restoration after network failure caused by cuts in fibre optic cables. We use this application to demonstrate the usefulness of traditional accelerated testing methods to test and estimate software reliability. These methods, which have been extensively used in hardware reliability, have an important role to play in software reliability assessment as well.