24,833 research outputs found

    Confidence Intervals for the Coefficient of Quartile Variation of a Zero-inflated Lognormal Distribution

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    There are many types of skewed distribution, one of which is the lognormal distribution that is positively skewed and may contain true zero values. The coefficient of quartile variation is a statistical tool used to measure the dispersion of skewed and kurtosis data. The purpose of this study is to establish confidence and credible intervals for the coefficient of quartile variation of a zero-inflated lognormal distribution. The proposed approaches are based on the concepts of the fiducial generalized confidence interval, and the Bayesian method. Coverage probabilities and expected lengths were used to evaluate the performance of the proposed approaches via Monte Carlo simulation. The results of the simulation studies show that the fiducial generalized confidence interval and the Bayesian based on uniform and normal inverse Chi-squared priors were appropriate in terms of the coverage probability and expected length, while the Bayesian approach based on Jeffreys' rule prior can be used as alternatives. In addition, real data based on the red cod density from a trawl survey in New Zealand is used to illustrate the performances of the proposed approaches. Doi: 10.28991/esj-2021-01289 Full Text: PD

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    āļšāļ—āļ„āļąāļ”āļĒāđˆāļ­āļ§āļąāļ•āļ–āļļāļ›āļĢāļ°āļŠāļ‡āļ„āđŒāļ‚āļ­āļ‡āļšāļ—āļ„āļ§āļēāļĄāļ—āļēāļ‡āļ§āļīāļŠāļēāļāļēāļĢāļ™āļĩāđ‰āđ€āļ›āđ‡āļ™āļāļēāļĢāļĻāļķāļāļĐāļēāļ§āļīāļ˜āļĩāļāļēāļĢāļ›āļĢāļ°āļĄāļēāļ“āļŠāđˆāļ§āļ‡āļ„āļ§āļēāļĄāđ€āļŠāļ·āđˆāļ­āļĄāļąāđˆāļ™āļ„āđˆāļēāļŠāļąāļĄāļ›āļĢāļ°āļŠāļīāļ—āļ˜āļīāđŒāļāļēāļĢāđāļ›āļĢāļœāļąāļ™āļ„āļ§āļ­āđ„āļ—āļĨāđŒāļ—āļąāđ‰āļ‡āļŦāļĄāļ” 3 āļ§āļīāļ˜āļĩāđ„āļ”āđ‰āđāļāđˆ 1) āļ§āļīāļ˜āļĩāđ‚āļšāđ€āļ™āđ‡āļ• 2) āļ§āļīāļ˜āļĩāļšāļđāļ•āļŠāđāļ•āļĢāļ› āđāļĨāļ° 3) āļ§āļīāļ˜āļĩāđ‚āļšāđ€āļ™āđ‡āļ•āļšāļđāļ•āļŠāđāļ•āļĢāļ› āđƒāļŠāđ‰āļāļēāļĢāļˆāļģāļĨāļ­āļ‡āļ‚āđ‰āļ­āļĄāļđāļĨāļˆāļēāļāļ›āļĢāļ°āļŠāļēāļāļĢāļ—āļĩāđˆāļĄāļĩāļāļēāļĢāđāļˆāļāđāļˆāļ‡ Normal(4,1), Lognormal(0,1) āđāļĨāļ° Gamma(1.5,1) āļ‚āļ™āļēāļ”āļ•āļąāļ§āļ­āļĒāđˆāļēāļ‡ 10, 25, 50 āđāļĨāļ° 100 āļ”āđ‰āļ§āļĒāļāļēāļĢāļ—āļģāļ‹āđ‰āļģāđ‚āļ”āļĒāđ€āļ—āļ„āļ™āļīāļ„āļĄāļ­āļ™āļ•āļīāļ„āļēāļĢāđŒāđ‚āļĨ āļœāļĨāļāļēāļĢāļĻāļķāļāļĐāļēāļžāļšāļ§āđˆāļē āļ§āļīāļ˜āļĩāļšāļđāļ•āļŠāđāļ•āļĢāļ›āđƒāļŦāđ‰āļ„āđˆāļēāļ›āļĢāļ°āļĄāļēāļ“āļ„āđˆāļēāļ„āļ§āļēāļĄāļ™āđˆāļēāļˆāļ°āđ€āļ›āđ‡āļ™āļ„āļĢāļ­āļšāļ„āļĨāļļāļĄāđ€āļ‚āđ‰āļēāđƒāļāļĨāđ‰āļĢāļ°āļ”āļąāļšāļ„āļ§āļēāļĄāđ€āļŠāļ·āđˆāļ­āļĄāļąāđˆāļ™āļ—āļĩāđˆāļāļģāļŦāļ™āļ”āđāļĨāļ°āđƒāļŦāđ‰āļ„āđˆāļēāļ„āļ§āļēāļĄāļĒāļēāļ§āđ€āļ‰āļĨāļĩāđˆāļĒāļ‚āļ­āļ‡āļŠāđˆāļ§āļ‡āļŠāļąāđ‰āļ™āļ—āļĩāđˆāļŠāļļāļ” āļĒāļāđ€āļ§āđ‰āļ™āđ€āļĄāļ·āđˆāļ­āļ‚āđ‰āļ­āļĄāļđāļĨāļĄāļĩāļāļēāļĢāđāļˆāļāđāļˆāļ‡āđāļšāļš Lognormal(0,1) āđāļĨāļ° Gamma(1.5,1) āđāļĨāļ°āļĄāļĩāļ‚āļ™āļēāļ”āļ•āļąāļ§āļ­āļĒāđˆāļēāļ‡āđ€āļ—āđˆāļēāļāļąāļš 100 āļ§āļīāļ˜āļĩāđ‚āļšāđ€āļ™āđ‡āļ•āļĄāļĩāļ›āļĢāļ°āļŠāļīāļ—āļ˜āļīāļ āļēāļžāļ„āļģāļŠāļģāļ„āļąāļ: āļšāļđāļ•āļŠāđāļ•āļĢāļ› āđ€āļ—āļ„āļ™āļīāļ„āļĄāļ­āļ™āļ•āļīāļ„āļēāļĢāđŒāđ‚āļĨAbstractThe purpose of this paper was to study the confidence intervals for a coefficient of quartile variation. The three methods were: 1) the Bonett method 2) the Bootstrap method and 3) the Bonett Bootstrap method. The study was carried out by generating random samples of 10, 25, 50 and 100 with Normal(4,1), Lognormal(0,1) and Gamma(0.5,1) distributions. The sample size and distribution were then checked for computing confidence intervals for a coefficient of quartile variation using Monte Carlo techniques. The result indicated that the bootstrap method provided the coverage probability close to the nominal level with the smallest average interval length for all sample sizes and all distributions. The Bonett method performed better when the distributions of the samples were Lognormal(0,1) and Gamma(0.5,1) with the size of 100.Keywords: Bootstrap, Monte Carlo Technique

    A stochastic sub-national population projection methodology with an application to the Waikato region of New Zealand

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    In this paper we use a stochastic population projection methodology at the sub-national level as an alternative to the conventional deterministic cohort-component method. We briefly evaluate the accuracy of previous deterministic projections and find that there is a tendency for these to be conservative: under-projecting fast growing populations and over-projecting slow growing ones. We generate probabilistic population projections for five demographically distinct administrative areas within the Waikato region of New Zealand, namely Hamilton City, Franklin District, Thames-Coromandel District, Otorohanga District and South Waikato District. Although spatial interaction between the areas is not taken into account in the current version of the methodology, a consistent set of cross-regional assumptions is used. The results are compared to official sub-national deterministic projections. The accuracy of sub-national population projections is in New Zealand strongly affected by the instability of migration as a component of population change. Unlike the standard cohort-component methodology, in which net migration levels are projected, the key parameters of our stochastic methodology are age-gender-area specific net migration rates. The projected range of rates of population growth is wider for smaller regions and/or regions more strongly affected by net migration. Generally, the identified and modelled uncertainty makes the traditional ‘mid range’ scenario of sub-national population projections of limited use for policy analysis or planning beyond a relatively short projection horizon. Directions for further development of a stochastic sub-national projection methodology are suggested

    A systematic review of the role of bisphosphonates in metastatic disease

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    Objectives: To identify evidence for the role of bisphosphonates in malignancy for the treatment of hypercalcaemia, prevention of skeletal morbidity and use in the adjuvant setting. To perform an economic review of current literature and model the cost effectiveness of bisphosphonates in the treatment of hypercalcaemia and prevention of skeletal morbidity Data sources: Electronic databases (1966-June 2001). Cochrane register. Pharmaceutical companies. Experts in the field. Handsearching of abstracts and leading oncology journals (1999-2001). Review methods: Two independent reviewers assessed studies for inclusion, according to predetermined criteria, and extracted relevant data. Overall event rates were pooled in a meta-analysis, odds ratios ( OR) were given with 95% confidence intervals (CI). Where data could not be combined, studies were reported individually and proportions compared using chi- squared analysis. Cost and cost-effectiveness were assessed by a decision analytic model comparing different bisphosphonate regimens for the treatment of hypercalcaemia; Markov models were employed to evaluate the use of bisphosphonates to prevent skeletal-related events (SRE) in patients with breast cancer and multiple myeloma. Results: For acute hypercalcaemia of malignancy, bisphosphonates normalised serum calcium in >70% of patients within 2-6 days. Pamidronate was more effective than control, etidronate, mithramycin and low-dose clodronate, but equal to high dose clodronate, in achieving normocalcaemia. Pamidronate prolongs ( doubles) the median time to relapse compared with clodronate or etidronate. For prevention of skeletal morbidity, bisphosphonates compared with placebo, significantly reduced the OR for fractures (OR [95% CI], vertebral, 0.69 [0.57-0.84], non-vertebral, 0.65 [0.54-0.79], combined, 0.65 [0.55-0.78]) radiotherapy 0.67 [0.57-0.79] and hypercalcaemia 0.54 [0.36-0.81] but not orthopaedic surgery 0.70 [0.46-1.05] or spinal cord compression 0.71 [0.47-1.08]. However, reduction in orthopaedic surgery was significant in studies that lasted over a year 0.59 [0.39-0.88]. Bisphosphonates significantly increased the time to first SRE but did not affect survival. Subanalyses were performed for disease groups, drugs and route of administration. Most evidence supports the use of intravenous aminobisphosphonates. For adjuvant use of bisphosphonates, Clodronate, given to patients with primary operable breast cancer and no metastatic disease, significantly reduced the number of patients developing bone metastases. This benefit was not maintained once regular administration had been discontinued. Two trials reported significant survival advantages in the treated groups. Bisphosphonates reduce the number of bone metastases in patients with both early and advanced breast cancer. Bisphosphonates are well tolerated with a low incidence of side-effects. Economic modelling showed that for acute hypercalcaemia, drugs with the longest cumulative duration of normocalcaemia were most cost-effective. Zoledronate 4 mg was the most costly, but most cost-effective treatment. For skeletal morbidity, Markov models estimated that the overall cost of bisphosphonate therapy to prevent an SRE was pound250 and pound1500 per event for patients with breast cancer and multiple myeloma, respectively. Bisphosphonate treatment is sometimes cost-saving in breast cancer patients where fractures are prevented. Conclusions: High dose aminobisphosphonates are most effective for the treatment of acute hypercalcaemia and delay time to relapse. Bisphosphonates significantly reduce SREs and delay the time to first SRE in patients with bony metastatic disease but do not affect survival. Benefit is demonstrated after administration for at least 6-12 months. The greatest body of evidence supports the use of intravenous aminobisphosphonates. Further evidence is required to support use in the adjuvant setting

    Evaluation of the East Bay Municipal Utility District's Pilot of WaterSmart Home Water Reports

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    This report presents the results of an independent evaluation of the East Bay Municipal Utility District's (EBMUD) year-long pilot project (Pilot) of WaterSmart Software's Home Water Reports (HWRs) service.The Pilot was intended to address three primary questions:First, would an SNB efficiency program like WaterSmart result in measurable reductionsin household water use?Second, would it increase rates of participation in other EBMUD conservation programs? Third, would it increase household knowledge and awareness of water consumption andways to use water more efficiently

    Differences in telomere length between sporadic and familial cutaneous melanoma

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    BACKGROUND: Several pieces of evidence indicate that a complex relationship exists between constitutional telomere length (TL) and the risk of cutaneous melanoma. Although the general perception is that longer telomeres increase melanoma risk, some studies do not support this association. We hypothesise that discordant data are due to the characteristics of the studied populations. OBJECTIVES: To evaluate the association of telomere length with familial and sporadic melanoma. METHODS: TL was measured by multiplex quantitative PCR in leukocytes from 310 melanoma patients according to familial/sporadic and single/multiple cancers and 216 age-matched controls. RESULTS: Patients with sporadic melanoma were found to have shorter telomeres as compared to those with familial melanoma. In addition, shorter telomeres, while tending to reduce the risk of familial melanoma regardless of single or multiple tumors, nearly trebled the risk of single sporadic melanoma. CONCLUSIONS: This is the first time that TL has been correlated to opposite effects on melanoma risk according to the presence or absence of familial predisposition. Individual susceptibility to melanoma should be taken into account when assessing the role of TL as a risk factor. This article is protected by copyright. All rights reserved

    Social health insurance

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    Temporal and spatial variability of snow accumulation in central Greenland

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    Snow accumulation records from central Greenland are explored to improve the understanding of the accumulation signal in Greenland ice core records. Results from a “forest” of 100 bamboo poles and automated accumulation monitors in the vicinity of Summit as well as shallow cores collected in the Summit and Crete areas are presented. Based on these accumulation data, a regression has been calculated to quantify the signal-to-noise variance ratio of ice core accumulation signals on a variety of temporal (1 week to 2 years) and spatial (20 m to 200 km) scales. Results are consistent with data obtained from year-round automated accumulation measurements deployed at Summit which suggest that it is impossible to obtain regional snow accumulation data with seasonal resolution using four accumulation monitors positioned over a length scale of ∾30 km. Given this understanding of the temporal and spatial dependence of noise in the ice core accumulation signal, the accumulation records from 17 shallow cores are revisited. Each core spans the time period from 1964 to 1983. By combining the accumulation records, the regional snow accumulation record has been obtained for this period. The results show that 9 of the 20 years can be identified as having an accumulation different from the 20 year mean with 99% confidence. The signal-to-noise variance ratio for the average accumulation signal sampled at annual intervals is 5.8±0.5. The averaged accumulation time series may be useful to climate modelers attempting to validate their models with accurate regional hydrologic data sets

    Age, SES, and Health: A Population Level Analysis of Health Inequalities over the Life Course

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    This paper tests two competing hypotheses on the relationship between age, SES, and health inequality at the cohort/population level. The accumulation hypothesis predicts that levels of SES- based health inequality and consequently overall health inequality within a cohort progressively increase as it ages. The divergence-convergence hypothesis predicts that these inequalities increase only up to early-old age then decrease. Data from a Canadian national health survey are used in this study, and are adjusted for SES-biases in mortality. Bootstrap methods are employed to assess the statistical precision and significance of the results. The Gini coefficient is used to estimate change in the overall level of health inequality with age and the Concentration coefficient estimates the contribution of SES- based health inequalities to this change. Health is measured using the Health Utilities Index and income and education provide the measure of SES. First, the findings show that the Gini coefficient progressively increases from 0.048 (95% CI: 0.045, 0.051) at ages 15-29 to 0.147 (95% CI: 0.131, 0.163) at ages 80+. Second, the data reveal that health inequalities between SES groups (Concentration coefficients for income and education) tend to follow a similar pattern of divergence. Together these findings provide support for the accumulation hypothesis. A notable implication of the study's findings is that the level of health inequality increases when compensating for age-specific socio- economic differences in mortality. These selective effects of mortality should be considered in future research on health inequalities and the life course.Health Inequality, Life Course, SES, Gini/Concentration coefficient
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