The Statistical Distribution of Incurred Losses and Its Evolution Over Time II: Parametric Models

1999 ◽  
Author(s):  
Greg Taylor
Keyword(s):  
Statistical Distribution ◽  
Parametric Models ◽  
Over Time

scholarly journals Trends in survival based on treatment modality in patients with pancreatic cancer: a population-based study

2020 ◽  
Vol 27 (1) ◽  
Author(s):  
S. Shakeel ◽  
C. Finley ◽  
G. Akhtar-Danesh ◽  
H. Y. Seow ◽  
N. Akhtar-Danesh
Keyword(s):  
Pancreatic Cancer ◽  
Treatment Modality ◽  
Survival Rates ◽  
Population Based ◽  
Parametric Models ◽  
Stage I ◽  
Analysis Survival ◽  
Long Term Prognosis ◽  
Over Time

Background Pancreatic cancer (PC) is one of the most lethal types of cancer and surgery remains the most optimal treatment modality for patients with resectable tumors. The objective of this study is to examine and compare the trends in survival rate among PC patients based on treatment modality.Methods This population-based retrospective analysis included all patients with known stage for PC in Ontario, Canada between 2007 and 2015. Flexible parametric models were used to conduct survival analysis. Survival rates were calculated based on treatment modality, while adjusting for patient and tumor specific covariates.Results In total, 6437 patients were included in this study. More than half of the patients aged 80 and over received no curative treatment. The proportion of patients receiving chemoradiation decreased over time. The 1-, 2- and 5-year survival rates increased 30-40% for stage I disease and less than 15% for stage II over the study period. Noticeable increases in 1-, 2, and 5-year survival rates were observed for patients underwent for distal pancreatectomy and Whipple procedures. There were no changes in survival for stage III and IV disease from 2007 to 2015.Conclusions A majority of cases for PC continue to be diagnosed in late stage, with poor short-term and long-term prognosis. The survival for stage I tumors and surgical modalities increased over time without any evidence of changes in stage distribution. We speculate that improvements in chemotherapy modalities and adoption of quality standards for surgical resection could be attributed for the positive trends in survival.

Something New, Something Old: Parametric Models for the Size of Distribution of Income

1997 ◽  
Author(s):  
Robert F. Bordley ◽  
James B. McDonald ◽  
Anand Mantrala
Keyword(s):  
Family Income ◽  
Probability Density Functions ◽  
Parametric Models ◽  
Density Functions ◽  
Lognormal Distributions ◽  
Special Cases ◽  
Income Data ◽  
Distribution Of Income ◽  
Generalized Beta Distribution ◽  
Over Time

Two new probability density functions (generalized beta and quadratic elasticity) are considered as models for the size distribution of income. The generalized beta distribution nests the generalized beta of the first and second kind, generalized gamma, lognormal and Pareto as well as introducing a number of new distributions to the literature. The quadratic elasticity distribution provides another generalization of the gamma distribution. The beta, gamma and lognormal distributions have been widely used in the income distribution literature. These distributions and many of their special cases are fit into five sets of US family income data for 1970, 1975, 1980, 1985, and 1990. This permits a comparison of the relative fit of several distributions over time.

scholarly journals Environmental Reliance Traps and Pathways – Theory and Analysis of Empirical Data From Rural Nepal

2020 ◽  
Vol 3 ◽  
Author(s):  
Solomon Zena Walelign ◽  
Xi Jiao ◽  
Carsten Smith-Hall
Keyword(s):  
Low Income ◽  
Household Income ◽  
Poverty Reduction ◽  
Market Access ◽  
Household Head ◽  
Empirical Work ◽  
Environmental Conservation ◽  
Parametric Models ◽  
Cash Income ◽  
Over Time

Existing theoretical and empirical work on poverty traps does not in detail investigate interactions between environmental reliance and socioeconomic factors over time. A string of studies has documented that environmental products provide rural households with both subsistence and cash income and that high environmental reliance is often associated with poverty. These studies are snapshots and do not allow an understanding of environmental reliance dynamics – are households trapped at high levels of environmental reliance, what factors enable movement from high to low reliance, and how are such movements associated with total household income? Here we develop and present a theory of environmental reliance traps that allows analysis and explanation of changes in household-level environmental reliance over time. We propose operational parametric and non-parametric models for empirical investigation of the theory and employ these using an environmentally augmented three-wave panel household income and asset dataset (n = 427, pooled n = 1212) from Nepal. We found no evidence of an environmental reliance trap in the study population, meaning that all households converged on a single long-term environmental reliance equilibrium point. Households with high environmental reliance moving down toward the equilibrium (n = 358) have low income and asset endowments; while households with low environmental reliance moving up toward the equilibrium (n = 854) are better off, in terms of both income and assets. The approach identified the poorer households that make a living from harvesting substantial amounts of environmental products The probability of being a high-downward moving household is negatively associated with the size of landholding, market access, and female headship, and positively associated with the household head being born in the village and belonging to the most common caste. We argue that the identification of environmental reliance pathways can simultaneously inform interventions aimed at environmental conservation and poverty reduction.

scholarly journals Age-Specific Rates of Onset of Cannabis Use in Mexico

2020 ◽  
Author(s):  
Mauricio López-Méndez ◽  
Angélica Ospina-Escobar ◽  
Rowan Iskandar ◽  
Fernando Alarid-Escudero
Keyword(s):  
Birth Cohort ◽  
Temporal Trends ◽  
Tobacco Consumption ◽  
Cannabis Use ◽  
Parametric Models ◽  
Birth Cohorts ◽  
Cross Sectional ◽  
Cannabis Consumption ◽  
Nationally Representative ◽  
Over Time

AbstractBackgroundOver the previous two decades, the prevalence of cannabis use has risen among the population in Mexico.AimsTo estimate the sex- and age-specific rates of onset of cannabis use over time.DesignTime-to-event flexible parametric models with spline specifications of the hazard function. Stratified analysis by sex, and control for temporal trends by year of data collection or decennial birth-cohort.SettingMexico.ParticipantsPooled sample of 141,342 respondents aged between 12 and 65 years from five nationally representative cross-sectional surveys, the Mexican National Surveys of Addictions (1998, 2002, 2008, 2012) and the Mexican National Survey on Drugs, Alcohol, and Tobacco Consumption (2016).MeasurementsWe estimated age-specific rates of onset of cannabis as the conditional rate of consuming cannabis for the first time at a specific age.FindingsAge-specific rates of onset of cannabis use per 1,000 individuals increased over time for both females and males. Peak rates per 1,000 ranged from 0.935 (95%CI= [0.754,1.140]) in 1998, to 5.390 (95%CI= [4.910,5.960]) in 2016 for females; and from 7.510 (95%CI= [5.516, 10.355]) in 1998, to 26.100 (95%CI= [23.162,30.169]) in 2016 for males. Across decennial birth-cohorts, peak rates of onset of cannabis use per 1,000 individuals for females ranged from 0.342 (95%CI= [0.127,0.898]) for those born in the 1930s, to 14.600 (95%CI= [13.200,16.100]) for those born in the 1990s; and for males, from 4.900 (95%CI= [0.768, 7.947]) for those born in the 1930s, to 38.700 (95%CI= [32.553,66.341]) for those born in the 1990s.ConclusionRates of onset of cannabis use for males are higher than for females; however, the change across recent cohorts of the rates of onset has increased at a faster rate among females. Our findings can inform and improve the implementation of policies around cannabis use by identifying subpopulations by age, sex, and birth-cohort that are at the highest risk of initiating cannabis consumption.

scholarly journals A Bayesian natural cubic B-spline varying coefficient method for non-ignorable dropout

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Camille M. Moore ◽  
Samantha MaWhinney ◽  
Nichole E. Carlson ◽  
Sarah Kreidler
Keyword(s):  
Clinical Trials ◽  
Viral Load ◽  
Drug Use ◽  
Cohort Studies ◽  
Cell Count ◽  
Parametric Model ◽  
Parametric Models ◽  
Viral Load Suppression ◽  
The Impact ◽  
Over Time

Abstract Background Dropout is a common problem in longitudinal clinical trials and cohort studies, and is of particular concern when dropout occurs for reasons that may be related to the outcome of interest. This paper reviews common parametric models to account for dropout and introduces a Bayesian semi-parametric varying coefficient model for exponential family longitudinal data with non-ignorable dropout. Methods To demonstrate these methods, we present results from a simulation study and estimate the impact of drug use on longitudinal CD4 + T cell count and viral load suppression in the Women’s Interagency HIV Study. Sensitivity analyses are performed to consider the impact of model assumptions on inference. We compare results between our semi-parametric method and parametric models to account for dropout, including the conditional linear model and a parametric frailty model. We also compare results to analyses that fail to account for dropout. Results In simulation studies, we show that semi-parametric methods reduce bias and mean squared error when parametric model assumptions are violated. In analyses of the Women’s Interagency HIV Study data, we find important differences in estimates of changes in CD4 + T cell count over time in untreated subjects that report drug use between different models used to account for dropout. We find steeper declines over time using our semi-parametric model, which makes fewer assumptions, compared to parametric models. Failing to account for dropout or to meet parametric assumptions of models to account for dropout could lead to underestimation of the impact of hard drug use on CD4 + cell count decline in untreated subjects. In analyses of subjects that initiated highly active anti-retroviral treatment, we find that the estimated probability of viral load suppression is lower in models that account for dropout. Conclusions Non-ignorable dropout is an important consideration when analyzing data from longitudinal clinical trials and cohort studies. While methods that account for non-ignorable dropout must make some unavoidable assumptions that cannot be verified from the observed data, many methods make additional parametric assumptions. If these assumptions are not met, inferences can be biased, making more flexible methods with minimal assumptions important.

Social transmission bias and the cultural evolution of folk-economic beliefs

2018 ◽  
Vol 41 ◽  
Author(s):  
David Hirshleifer ◽  
Siew Hong Teoh
Keyword(s):  
Cultural Evolution ◽  
Social Transmission ◽  
Cognitive Approach ◽  
Economic Problems ◽  
Economic Attitudes ◽  
The Social ◽  
Economic Beliefs ◽  
Over Time

AbstractEvolved dispositions influence, but do not determine, how people think about economic problems. The evolutionary cognitive approach offers important insights but underweights the social transmission of ideas as a level of explanation. The need for asocialexplanation for the evolution of economic attitudes is evidenced, for example, by immense variations in folk-economic beliefs over time and across individuals.

Articulatory Generalization in Two Word-Medial, Ambisyllabic Contexts

1988 ◽  
Vol 19 (3) ◽  
pp. 251-258 ◽  
Author(s):  
Virginia I. Wolfe ◽  
Suzanne D. Blocker ◽  
Norma J. Prater
Keyword(s):  
Common View ◽  
Perceptual Salience ◽  
The Common ◽  
Unitary Concept ◽  
Over Time

Articulatory generalization of velar cognates /k/, /g/ in two phonologically disordered children was studied over time as a function of sequential word-morpheme position training. Although patterns of contextual acquisition differed, correct responses to the word-medial, inflected context (e.g., "picking," "hugging") occurred earlier and exceeded those to the word-medial, noninflected context (e.g., "bacon," "wagon"). This finding indicates that the common view of the word-medial position as a unitary concept is an oversimplification. Possible explanations for superior generalization to the word-medial, inflected position are discussed in terms of coarticulation, perceptual salience, and the representational integrity of the word.

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