Random Number Generators

The quasi-negative-binomial distribution was applied to queuing theory for determining the distribution of total number of customers served before the queue vanishes under certain assumptions. Some structural properties (probability generating function, convolution, mode and recurrence relation) for the moments of quasi-negative-binomial distribution are discussed. The distribution’s characterization and its relation with other distributions were investigated. A computer program was developed using R to obtain ML estimates and the distribution was fitted to some observed sets of data to test its goodness of fit

Mortality in Transition: Study Protocol of the PrivMort Project, a multilevel convenience cohort study

Background: Previous research using routine data identified rapid mass privatisation as an important driver of mortality crisis following the collapse of Communism in Central and Eastern Europe. However, existing studies on the mortality crisis relying on individual level or routine data cannot assess both distal (societal) and proximal (individual) causes of mortality simultaneously. The aim of the PrivMort Project is to overcome these limitations and to investigate the role of societal factors (particularly rapid mass privatisation) and individual-level factors (e.g. alcohol consumption) in the mortality changes in post-communist countries. Methods: The PrivMort conducts large-sample surveys in Russia, Belarus and Hungary. The approach is unique in comparing towns that have undergone rapid privatisation of their key industrial enterprises with those that experienced more gradual forms of privatisation, employing a multi-level retrospective cohort design that combines data on the industrial characteristics of the towns, socio-economic descriptions of the communities, settlement-level data, individual socio-economic characteristics, and individuals’ health behaviour. It then incorporates data on mortality of different types of relatives of survey respondents, employing a retrospective demographic approach, which enables linkage of historical patterns of mortality to exposures, based on experiences of family members. By May 2016, 63,073 respondents provided information on themselves and 205,607 relatives, of whom 102,971 had died. The settlement-level dataset contains information on 539 settlements and 12,082 enterprises in these settlements in Russia, 96 settlements and 271 enterprises in Belarus, and 52 settlement and 148 enterprises in Hungary. Discussion: In addition to reinforcing existing evidence linking smoking, hazardous drinking and unemployment to mortality, the PrivMort dataset will investigate the variation in transition experiences for individual respondents and their families across settlements characterized by differing contextual factors, including industrial characteristi

Advances in the Measurement of Adult Mortality from Data on Orphanhood

The premature death of adults is a major, but poorly documented, health problem in developing countries. The inadequacy of registration statistics and difficulty of collecting accurate data directly in surveys mean that indirect methods of analysis, particularly those based on orphanhood, represent an important source of adult mortality estimates. Assessments of the orphanhood method have expressed concern about the robustness of the procedures used to estimate life table indices from orphanhood data, particularly for males, about under-reporting of orphanhood, particularly among children (the ‘adoption effect’), and about the ways that complete life tables are derived from indirect estimates. Investigation of the estimation procedures suggests that they are very robust for female mortality and acceptably so for male mortality. Small increases in accuracy would accrue from use of a regression based method to estimate male mortality, that incorporates a more sophisticated fertility model than the original method. Such a procedure is presented, together with one for female mortality based on consistent assumptions. Existing methods for fitting life tables to indirect estimates are sometimes less satisfactory. An alternative approach is proposed and assessed. In some countries, orphanhood estimates are seriously biased by the adoption effect. Such errors can be reduced by techniques that analyze data on orphanhood in adulthood. Two such methods are developed and tested. The first estimates mortality from period data on orphanhood after age 20; the second uses data on orphanhood since first marriage. The methods are sensitive to age exaggeration, but data on young adults are a promising source of recent estimates of adult mortality. Finally, procedures are presented for analyzing data on orphanhood prior to marriage. In countries where adults report this information accurately, it can be used to measure adult mortality up to 35 years before the data were collected

Advantages and insights from a hierarchical Bayesian growth and dynamics model based on salmonid electrofishing removal data

Growth is a fundamental ecological process of stream-dwelling salmonids which is strongly interrelated to critical life history events (emergence, mortality, sexual maturity, smolting, spawning). The ability to accurately model growth becomes critical when making population predictions over large temporal (multi-decadal) and spatial (meso) scales, e.g., investigating the effect of global change. Body length collection by removal sampling is a widely-used practice for monitoring fish populations over such large scales. Such data can be efficiently integrated into a Hierarchical Bayesian Model (HBM) and lead to interesting findings on fish dynamics. We illustrate this approach by presenting an integrated HBM of brown trout (Salmo trutta) growth, population dynamics, and removal sampling data collection processes using large temporal and spatial scales data (20 years; 48 sites placed along a 100 km latitudinal gradient). Growth and population dynamics are modelled by ordinary differential equations with parameters bound together in a hierarchical structure. The observation process is modelled with a combination of a Poisson error, a binomial error, and a mixture of Gaussian distributions. Absolute fit is measured using posterior predictive checks, which results indicate that our model fits the data well. Results indicate that growth rate is positively correlated to catchment area. This result corroborates those of other studies (laboratory, exploratory) that identified factors besides water temperature that are related to daily ration and have a significant effect on stream-dwelling salmonid growth at a large scale. Our study also illustrates the value of integrated HBM and electrofishing removal sampling data to study in situ fish populations over large scales

Contributions to the early life histories of alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis): Rearing, identification, ageing, and ecology

Early life histories of alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis), collectively known as river herring, are poorly documented for Chesapeake Bay populations. Improved knowledge of these early life histories potentially will aid fisheries, habitat and resource management. Investigations were conducted following two lines. First, alewife and blueback herring larvae reared from eggs were used to investigate methods for species identification and to validate the otolith increment method for age determination. Blueback herring larvae hatched from naturally-spawned eggs were reared to age 24 d. Alewife and blueback herring larvae hatched from artificially-spawned eggs were reared to age 32 d and age 37 d. Alewife larvae exhibited paired melanophores laterally along the notochord starting at about 15 mm SL, contracted xanthophores dorsally on the head, and lacked xanthochrome at the caudal fin base. Blueback herring exhibited one or two melanophores dorsally on the notochord starting at about 11 mm SL, relatively large xanthophores dorsally on the head, and xanthochrome at the caudal fin base. Other pigment variation was found. Estimated deposition of otolith increments was 1.16 and 0.90 increment d&\sp{lcub}-1{rcub}& for blueback herring larvae and 0.90 increment d&\sp{lcub}-1{rcub}& for alewife larvae. Increment enumeration was affected by otolith microstructure appearance, but estimated deposition did not differ statistically from one increment d&\sp{lcub}-1{rcub}&. Second, larval river herring distributions, abundances, growth rates, and hatch dates in the Pamunkey River tidal freshwater reach were analyzed. Distributions and abundances of zooplankton prey for river herring larvae were also analyzed. High abundances in two tidal creeks suggested that larvae occur in these areas from about late April to about mid-May. Larval river herring growth, pooled across seasons, was faster in the tidal creeks, 0.46 mm d&\sp{lcub}-1{rcub}&, than the mainstem river, 0.34 mm d&\sp{lcub}-1{rcub}&. Faster growth in the tidal creeks may increase survival by reducing the larval stage duration. Older larvae, pooled across habitats, grew faster than younger larvae, 0.59 mm d&\sp{lcub}-1{rcub}& and 0.35 mm d&\sp{lcub}-1{rcub}&. Larvae with relatively earlier hatch dates were associated primarily with the mainstem river while larvae with relatively later hatch dates were associated primarily with the tidal creeks. Zooplankton abundances were higher in the tidal creeks than the mainstem river