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Statistical Evidence (statistical + evidence)
Kinds of Statistical Evidence Selected AbstractsPiece Rates, Fixed Wages, and Incentive Effects: Statistical Evidence from Payroll RecordsINTERNATIONAL ECONOMIC REVIEW, Issue 1 2000Harry J. Paarsch We develop and estimate an agency model of worker behavior under piece rates and fixed wages. The model implies optimal decision rules for the firm's choice of a compensation system as a function of working conditions. Our model also implies an upper and lower bound to the incentive effect (the productivity gain realized by paying workers piece rates rather than fixed wages) that can be estimated using regression methods. Using daily productivity data collected from the payroll records of a British Columbia tree-planting firm, we estimate these bounds to be an 8.8 and a 60.4 percent increase in productivity. Structural estimation, which accounts for the firm's optimal choice of a compensation system, suggests that incentives caused a 22.6 percent increase in productivity. However, only part of this increase represents valuable output because workers respond to incentives, in part, by reducing quality. [source] Interpreting Statistical Evidence with Empirical Likelihood FunctionsBIOMETRICAL JOURNAL, Issue 4 2009Zhiwei Zhang Abstract There has been growing interest in the likelihood paradigm of statistics, where statistical evidence is represented by the likelihood function and its strength is measured by likelihood ratios. The available literature in this area has so far focused on parametric likelihood functions, though in some cases a parametric likelihood can be robustified. This focused discussion on parametric models, while insightful and productive, may have left the impression that the likelihood paradigm is best suited to parametric situations. This article discusses the use of empirical likelihood functions, a well-developed methodology in the frequentist paradigm, to interpret statistical evidence in nonparametric and semiparametric situations. A comparative review of literature shows that, while an empirical likelihood is not a true probability density, it has the essential properties, namely consistency and local asymptotic normality that unify and justify the various parametric likelihood methods for evidential analysis. Real examples are presented to illustrate and compare the empirical likelihood method and the parametric likelihood methods. These methods are also compared in terms of asymptotic efficiency by combining relevant results from different areas. It is seen that a parametric likelihood based on a correctly specified model is generally more efficient than an empirical likelihood for the same parameter. However, when the working model fails, a parametric likelihood either breaks down or, if a robust version exists, becomes less efficient than the corresponding empirical likelihood. [source] The Likelihood as Statistical Evidence in Multiple Comparisons in Clinical Trials: No Free LunchBIOMETRICAL JOURNAL, Issue 3 2006Edward L. Korn Abstract The likelihood ratio summarizes the strength of statistical evidence for one simple pre-determined hypothesis versus another. However, it does not directly address the multiple comparisons problem. In this paper we discuss some concerns related to the application of likelihood ratio methods to several multiple comparisons issues in clinical trials, in particular, subgroup analysis, multiple variables, interim monitoring, and data driven choice of hypotheses. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Statistical evidence and compliance with Title IXNEW DIRECTIONS FOR INSTITUTIONAL RESEARCH, Issue 138 2008John J. Cheslock This chapter examines the statistical evidence used to determine whether an institution's athletic program is in compliance with Title IX. [source] Statistical evidence in medical trials: what do the data really tell us?PHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 2 2007$44.50 Oxford University Press; http://www.oup.com/, Simon SD (2006) ISBN: 0198567618; 216 pages; £25.00 No abstract is available for this article. [source] The contribution of intracellular calcium stores to mEPSCs recorded in layer II neurones of rat barrel cortexTHE JOURNAL OF PHYSIOLOGY, Issue 2 2002Christopher R. L. Simkus Loading slices of rat barrel cortex with 50 ,m BAPTA-AM while recording from pyramidal cells in layer II induces a marked reduction in both the frequency and amplitudes of mEPSCs. These changes are due to a presynaptic action. Blocking the refilling of Ca2+ stores with 20 ,m cyclopiazonic acid (CPA), a SERCA pump inhibitor, in conjunction with neuronal depolarisation to activate Ca2+ stores, results in a similar reduction of mEPSCs to that observed with BAPTA-AM, indicating that the source for intracellular Ca2+ is the endoplasmic reticulum. Block or activation of ryanodine receptors by 20 ,m ryanodine or 10 mm caffeine, respectively, shows that a significant proportion of mEPSCs are caused by Ca2+ release from ryanodine stores. Blocking IP3 receptors with 14 ,m 2-aminoethoxydiphenylborane (2APB) also reduces the frequency and amplitude of mEPSCs, indicating the involvement of IP3 stores in the generation of mEPSCs. Activation of group I metabotropic receptors with 20 ,m (RS) -3,5-dihydroxyphenylglycine (DHPG) results in a significant increase in the frequency of mEPSCs, further supporting the role of IP3 receptors and indicating a role of group I metabotropic receptors in causing transmitter release. Statistical evidence is presented for Ca2+ -induced Ca2+ release (CICR) from ryanodine stores after the spontaneous opening of IP3 stores. [source] WHY HAS CRIME FALLEN?ECONOMIC AFFAIRS, Issue 3 2002AN ECONOMIC PERSPECTIVE In this paper we consider the reasons why the general level of recorded crime has been falling in the United States and many European countries in the last ten years. We review the time-series statistical evidence on the determinants of crime, and investigate the extent to which these determinants are matched with survey evidence on the offending behaviour of young people. This survey evidence is particularly revealing on the perceptions of young people to various sorts of deterrents, and it also highlights a strong association between illicit drug use and involvement in crime. [source] LIVE-BIRTH IN VIPERS (VIPERIDAE) IS A KEY INNOVATION AND ADAPTATION TO GLOBAL COOLING DURING THE CENOZOICEVOLUTION, Issue 9 2009Vincent J. Lynch The identification of adaptations and key innovations has long interested biologists because they confer on organisms the ability to exploit previously unavailable ecological resources and respond to novel selective pressures. Although it can be extremely difficult to test for the effects of a character on the rate of lineage diversification, the convergent evolution of a character in multiple lineages provides an excellent opportunity to test for the effect of that character on lineage diversification. Here, I examine the effect of parity mode on the diversification of vipers, which have independently evolved viviparity in at least 13 lineages. I find strong statistical evidence that viviparous species diversify at a greater rate than oviparous species and correlate major decreases in the diversification rate of oviparous species with periods of global cooling, such as the Oligocene. These results suggest that the evolution of viviparity buffered live-bearing species against the negative effects of global climate change during the Cenozoic, and was a key innovation in the evolution and diversification of live-bearing vipers. [source] The relationship between performance appraisal criterion specificity and statistical evidence of discriminationHUMAN RESOURCE MANAGEMENT, Issue 2 2003H. W. Hennessey Jr. Plaintiffs' expert witnesses in EEO cases involving performance appraisals often claim that adverse impact is a result of the type of rating format used. Their theory is that more specific rating criteria will lead to lessened adverse impact. We tested that theory by comparing data from a simple category-based rating system against data from a standards-based Work Planning and Review appraisal system with over 248,000 performance appraisals of state employees. Using logistic regression and statistical definitions of prima facie discrimination, we found no support for the hypothesis that adverse impact is materially affected by criterion specificity. © 2003 Wiley Periodicals, Inc. [source] Domestic Crony Capitalism and International Fickle Capital: Is There a Connection?INTERNATIONAL FINANCE, Issue 1 2001Shang-Jin WeiArticle first published online: 16 DEC 200 Domestic crony capitalism and fickle international capital flows are often suggested as two rival explanations for currency crises. This article examines a possible linkage between the two that has not been explored much in the literature: domestic crony capitalism may make a country more dependent on the more fickle type of international capital flows (e.g. international bank loans) rather than the less volatile type (e.g. foreign direct investment). It presents statistical evidence that the degree of domestic crony capitalism is indeed associated with a higher external loan-to-FDI ratio. Such a composition of capital flows has been identified as being associated with a higher incidence of a currency crisis. Therefore, even though crony capitalism does not forecast the exact timing of a crisis, it can nevertheless increase its likelihood. [source] Damage Control Productivity: An Input Damage Abatement ApproachJOURNAL OF AGRICULTURAL ECONOMICS, Issue 3 2001Alfons Oude Lansink This paper compares the value of the marginal product of three different pesticides from different specifications of the production function. The specifications are the output damage abatement specification proposed by Lichtenberg and Zilberman, a general input damage abatement specification and a traditional production function. These specifications are estimated on panel data of specialised Dutch arable farms over the period 1989,1992, using Generalised Maximum Entropy estimation. Results of the input damage abatement specification show that pesticides have different impacts on individual productive inputs, although statistical evidence is weak. The output damage abatement specification produces statistically more significant relations, but imposes restrictions that are only partly supported by the data. It is also found that estimation of a quadratic traditional production function, that treats damage abatement inputs in the same way as productive inputs, does not lead to over estimation of the value of the marginal product as previous authors have hypothesised. [source] Social Network Profiles as Taste PerformancesJOURNAL OF COMPUTER-MEDIATED COMMUNICATION, Issue 1 2008Hugo Liu This study examines how a social network profile's lists of interests,music, books, movies, television shows, etc.,can function as an expressive arena for taste performance. By composing interest tokens around a theme, profile users craft their "taste statements." First, socioeconomic and aesthetic influences on taste are considered, and the expressivity of interest tokens is analyzed using a semiotic framework. Then, a grounded theory approach is taken to identify four types of taste statements,those that convey prestige, differentiation, authenticity, and theatrical persona. The semantics of taste and taste statements are further investigated through a statistical analysis of 127,477 profiles collected from the MySpace social network site between November 2006 and January 2007. The major findings of the analysis include statistical evidence for prestige and differentiation taste statements and an interpretation of the taste semantics underlying the MySpace community,its motifs, paradigms, and demographic structures. [source] Hepatic coccidiosis of the blue whiting, Micromesistius poutassou (Risso), and horse mackerel, Trachurus trachurus (L.), from Galician watersJOURNAL OF FISH DISEASES, Issue 6 2001E Abollo The aetiology, epidemiology and pathology of coccidiosis in commercially-exploited populations of Micromesistius poutassou and Trachurus trachurus from Galician waters were investigated. Sporogonic stages of Goussia clupearum and G. cruciata were found in the liver. Although the descriptive statistics of Goussia infrapopulations and demographic infection values were always higher in M. poutassou than in T. trachurus, parasite distribution was highly skewed for both coccidian species. In both fish species, the number of oöcysts showed a similar cumulative effect as parasite counts increased with increasing length and weight of fish, but did not change with host sex or sexual maturity. Pathological changes in infected liver parenchyma of both species were moderate (in T. trachurus) to severe (in M. poutassou), with greatly reduced livers in the most heavily infected fish. Large areas of liver tissue were replaced with oöcysts. Host response to infection included the formation of a fibrous capsule prior to infiltration by melanin and lymphocytes. Although post-recruit individuals of both fish species apparently tolerate a severe infection, there was statistical evidence of a serious contribution by the parasite to poor body condition in M. poutassou shown by changes in the hepatosomatic and K-Fulton indices and in the length- to-weight relationship. [source] Burned by Bullying in the American Workplace: Prevalence, Perception, Degree and Impact*JOURNAL OF MANAGEMENT STUDIES, Issue 6 2007Pamela Lutgen-Sandvik abstract This study assesses the prevalence of workplace bullying in a sample of US workers, using a standardized measure of workplace bullying (Negative Acts Questionnaire, NAQ), and compares the current study's prevalence rates with those from other bullying and aggression studies. The article opens by defining bullying as a persistent, enduring form of abuse at work and contrasting it with other negative workplace actions and interactions. Through a review of the current literature, we propose and test hypotheses regarding bullying prevalence and dynamics relative to a sample of US workers. After discussing research methods, we report on the rates of bullying in a US sample, compare these to similar studies, and analyse the negative acts that might lead to perceptions of being bullied. Based upon past conceptualizations, as well as research that suggests bullying is a phenomenon that occurs in gradations, we introduce and provide statistical evidence for the construct and impact of bullying degree. Finally, the study explores the impact of bullying on persons who witnessed but did not directly experience bullying in their jobs. [source] The SCUBA Half-Degree Extragalactic Survey (SHADES) , VIII.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008SWIRE, SXDF surveys, The nature of faint submillimetre galaxies in SHADES ABSTRACT We present the optical-to-submillimetre spectral energy distributions (SEDs) for 33 radio and mid-infrared (mid-IR) identified submillimetre galaxies discovered via the SHADES 850-,m SCUBA imaging in the Subaru- XMM Deep Field (SXDF). Optical data for the sources come from the SXDF and mid- and far-IR fluxes from SWIRE. We obtain photometric redshift estimates for our sources using optical and IRAC 3.6- and 4.5-,m fluxes. We then fit SED templates to the longer wavelength data to determine the nature of the far-IR emission that dominates the bolometric luminosity of these sources. The IR template fits are also used to resolve ambiguous identifications and cases of redshift aliasing. The redshift distribution obtained broadly matches previous results for submillimetre sources and on the SHADES SXDF field. Our template fitting finds that active galactic nuclei, while present in about 10 per cent of our sources, do not contribute significantly to their bolometric luminosity. Dust heating by starbursts, with either Arp220 or M82 type SEDs, appears to be responsible for the luminosity in most sources (23/33 are fitted by Arp220 templates, 2/33 by the warmer M82 templates). 8/33 sources, in contrast, are fitted by a cooler cirrus dust template, suggesting that cold dust has a role in some of these highly luminous objects. Three of our sources appear to have multiple identifications or components at the same redshift, but we find no statistical evidence that close associations are common among our SHADES sources. Examination of rest-frame K -band luminosity suggests that ,downsizing' is underway in the submillimetre galaxy population, with lower redshift systems lying in lower mass host galaxies. Of our 33 identifications six are found to be of lower reliability but their exclusion would not significantly alter our conclusions. [source] Are Reports of Discrimination Valid?AMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 2 2008Considering the Moral Hazard Effect Antidiscrimination laws are designed to prompt employers to stop excluding black workers from jobs they offer and from treating them unequally with respect to promotion and salaries once on the job. However, a moral hazard effect can arise if the existence of the laws leads black employees to bring unjustified claims of discrimination against employers. It has been argued that employers may become more reluctant to hire black workers for fear of being subjected to frivolous lawsuits. Using the Multi-City Study of Urban Inequality (MCSUI), we find that male and female black workers are far more likely than whites to report racial discrimination at work. This is the case even when a host of human capital and labor market factors are controlled for. Further, nearly all black workers who report they have been discriminated against on the job in the MCSUI Surveys also show statistical evidence of wage discrimination. This is not the case for white males or females. We find little evidence to support a moral hazard effect. [source] Fiscal Coordination and Financial Dependence of State Governments in MexicoPUBLIC BUDGETING AND FINANCE, Issue 3 2010JORGE IBARRA-SALAZAR This paper presents evidence of the effects on subnational financial dependence of the intergovernmental fiscal agreement implemented in 1980. In contrast with a previous study that uses annual time series national data, we use a panel of annual time series (1975,1995) of 31 Mexican states. We propose and estimate three different empirical models using the fixed effects panel data approach. In concordance with previous literature, we find strong statistical evidence that the implementation of the agreement increased financial dependence. The main contribution of this paper is to distinguish the effect of the 1980 fiscal arrangement on every state's degree of financial dependence. [source] Partisan Waves: International Business Cycles and Electoral ChoiceAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 4 2009Mark Andreas Kayser Pundits have often claimed, but scholars have never found, that partisan swings in the vote abroad predict electoral fortunes at home. Employing semiannual Eurobarometer data on vote intention in eight European countries, this article provides statistical evidence of international comovement in partisan vote intention and its provenance in international business cycles. Electoral support for "luxury parties," those parties associated with higher spending and taxation, covaries across countries together with the business cycle. Both the domestic and international components of at least one economic aggregate,unemployment,prove a strong predictor of shifts in domestic vote intention. Globalization, by driving business cycle integration, is also synchronizing partisan cycles. [source] Recursive Modeling of Nonlinear Dynamics in UK Stock ReturnsTHE MANCHESTER SCHOOL, Issue 4 2003Massimo Guidolin This paper presents results from recursive modeling of nonlinear dynamics in UK stock returns. A specification search suggests a two-state model and we demonstrate the ability of this model to capture time-varying volatility, skew and kurtosis in UK stock returns. An out-of-sample forecasting experiment confirms the strong statistical evidence of nonlinearity and shows that accounting for regimes leads to improved forecasting performance. [source] Genetic mapping of quantitative trait loci affecting susceptibility in chicken to develop pulmonary hypertension syndromeANIMAL GENETICS, Issue 6 2005T. S. K. M. Rabie Summary Pulmonary hypertension syndrome (PHS), also referred to as ascites syndrome, is a growth-related disorder of chickens frequently observed in fast-growing broilers with insufficient pulmonary vascular capacity at low temperature and/or at high altitude. A cross between two genetically different broiler dam lines that originated from the White Plymouth Rock breed was used to produce a three-generation population. This population was used for the detection and localization of quantitative trait loci (QTL) affecting PHS-related traits. Ten full-sib families consisting of 456 G2 birds were typed with 420 microsatellite markers covering 24 autosomal chromosomes. Phenotypic observations were collected on 4202 G3 birds and a full-sib across family regression interval mapping approach was used to identify QTL. There was statistical evidence for QTL on chicken chromosome 2 (GGA2), GGA4 and GGA6. Suggestive QTL were found on chromosomes 5, 8, 10, 27 and 28. The most significant QTL were located on GGA2 for right and total ventricular weight as percentage of body weight (%RV and %TV respectively). A related trait, the ratio of right ventricular weight as percentage to total ventricular weight (RATIO), reached the suggestive threshold on this chromosome. All three QTL effects identified on GGA2 had their maximum test statistic in the region flanked by markers MCW0185 and MCW0245 (335,421 cM). [source] The use of long PCR to confirm three common alleles at the CYP2A6 locus and the relationship between genotype and smoking habitANNALS OF HUMAN GENETICS, Issue 5 2000D. F. GU Long PCR followed by nested PCR has previously been used to determine CYP2A6 160H alleles, but the method proved unreliable. We have optimized this approach in a DNA bank of 1032 subjects (age range 59,74 years) to give reliable results, yielding indirect molecular evidence and very strong statistical evidence of hitherto unrecognized common alleles (designated O) recalcitrant to the long PCR. Coding three alleles (160L, 160H and O) and an approach to association analysis originally developed to deal with null alleles implicit in ABO blood group phenotyping, the contribution of 160H (functionally null) to reduced smoking habit has been clearly measured for the first time, unconfounded by alleles null to the long PCR. The most significant findings (p < 0.01) are that the possession of a 160H allele, compared with not possessing a 160H allele, is associated with a mean age of starting regular smoking 3 years later (95% CI±1.93 years, average start age 20,21 years rather than 17,18 years); and that the average likelihood of quitting smoking at any time is 1.75 fold (95% CI. 1.17,2.61) for those possessing an 160H allele compared with those who have no 160H allele. This suggests that a smoking subject with a genotype predicted to confer 50% of the ability to eliminate nicotine via the CYP2A6 pathway has almost twice the likelihood of quitting smoking. [source] POISSON VERSUS BINOMIAL: APPOINTMENT OF JUDGES TO THE U.S. SUPREME COURTAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2010Vassilly Voinov Summary The problem of discriminating between the Poisson and binomial models is discussed in the context of a detailed statistical analysis of the number of appointments of the U.S. Supreme Court justices from 1789 to 2004. Various new and existing tests are examined. The analysis shows that both simple Poisson and simple binomial models are equally appropriate for describing the data. No firm statistical evidence in favour of an exponential Poisson regression model was found. Two attendant results were obtained by simulation: firstly, that the likelihood ratio test is the most powerful of those considered when testing for the Poisson versus binomial and, secondly, that the classical variance test with an upper-tail critical region is biased. [source] Interpreting Statistical Evidence with Empirical Likelihood FunctionsBIOMETRICAL JOURNAL, Issue 4 2009Zhiwei Zhang Abstract There has been growing interest in the likelihood paradigm of statistics, where statistical evidence is represented by the likelihood function and its strength is measured by likelihood ratios. The available literature in this area has so far focused on parametric likelihood functions, though in some cases a parametric likelihood can be robustified. This focused discussion on parametric models, while insightful and productive, may have left the impression that the likelihood paradigm is best suited to parametric situations. This article discusses the use of empirical likelihood functions, a well-developed methodology in the frequentist paradigm, to interpret statistical evidence in nonparametric and semiparametric situations. A comparative review of literature shows that, while an empirical likelihood is not a true probability density, it has the essential properties, namely consistency and local asymptotic normality that unify and justify the various parametric likelihood methods for evidential analysis. Real examples are presented to illustrate and compare the empirical likelihood method and the parametric likelihood methods. These methods are also compared in terms of asymptotic efficiency by combining relevant results from different areas. It is seen that a parametric likelihood based on a correctly specified model is generally more efficient than an empirical likelihood for the same parameter. However, when the working model fails, a parametric likelihood either breaks down or, if a robust version exists, becomes less efficient than the corresponding empirical likelihood. [source] The Likelihood as Statistical Evidence in Multiple Comparisons in Clinical Trials: No Free LunchBIOMETRICAL JOURNAL, Issue 3 2006Edward L. Korn Abstract The likelihood ratio summarizes the strength of statistical evidence for one simple pre-determined hypothesis versus another. However, it does not directly address the multiple comparisons problem. In this paper we discuss some concerns related to the application of likelihood ratio methods to several multiple comparisons issues in clinical trials, in particular, subgroup analysis, multiple variables, interim monitoring, and data driven choice of hypotheses. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Utilities of the P -value Distribution Associated with Effect Size in Clinical Trials,BIOMETRICAL JOURNAL, Issue 6 2003H.M. James Hung Abstract The P -value, which is widely used for assessing statistical evidence in randomized comparative clinical trials, is a function of the observed effect size of the experimental treatment relative to the control treatment. The relationship of the P -value with the observed effect size at study completion and the effect size anticipated at the design stage has potential usefulness in providing guidance for planning and interpretation of a clinical trial. The post-trial power associated with a statistically significant P -value from a completed study is also a random variable and its use may assist in planning a follow-up trial to confirm the statistically significant findings in an initial study. A measure of robustness is explored to quantify the degree of sensitivity of the observed P -value to potential bias that may be contained in the observed effect size. [source] A Test for Constant Fatality Rate of an Emerging Epidemic: With Applications to Severe Acute Respiratory Syndrome in Hong Kong and BeijingBIOMETRICS, Issue 3 2008K. F. Lam Summary The etiology, pathogenesis, and prognosis for a newly emerging disease are generally unknown to clinicians. Effective interventions and treatments at the earliest possible times are warranted to suppress the fatality of the disease to a minimum, and inappropriate treatments should be abolished. In this situation, the ability to extract most information out of the data available is critical so that important decisions can be made. Ineffectiveness of the treatment can be reflected by a constant fatality over time while effective treatment normally leads to a decreasing fatality rate. A statistical test for constant fatality over time is proposed in this article. The proposed statistic is shown to converge to a Brownian motion asymptotically under the null hypothesis. With the special features of the Brownian motion, we are able to analyze the first passage time distribution based on a sequential tests approach. This allows the null hypothesis of constant fatality rate to be rejected at the earliest possible time when adequate statistical evidence accumulates. Simulation studies show that the performance of the proposed test is good and it is extremely sensitive in picking up decreasing fatality rate. The proposed test is applied to the severe acute respiratory syndrome data in Hong Kong and Beijing. [source] Pharmacokinetics of sildenafil after single oral doses in healthy male subjects: absolute bioavailability, food effects and dose proportionalityBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 2002Donald J. Nichols Aims, To determine the absolute bioavailability, dose proportionality and the effects of food on the pharmacokinetics of single oral doses of sildenafil citrate. Methods, Three open-label, randomized crossover studies were conducted in healthy male subjects. Absolute bioavailability was determined by comparing pharmacokinetic data after administration of single oral and intravenous 50-mg doses of sildenafil (n=12 subjects). Food effects were examined by comparing pharmacokinetic data for sildenafil and its primary circulating metabolite, UK-103,320, after administration of a single oral 100-mg dose in the fasted and fed states (n=34 subjects). Dose proportionality was assessed from pharmacokinetic data obtained after administration of four single oral doses of sildenafil (25, 50, 100 and 200 mg) to 32 subjects. The safety and tolerability of sildenafil were also assessed in all of these studies. Results, The calculated absolute oral bioavailability of sildenafil was 41% (90% CI: 36,47). Food slowed the rate of absorption, delaying mean tmax by approximately 1 h and reducing Cmax by 29% (90% CI: 19,38). Systemic exposure, as assessed by the mean area under the plasma concentration,time curve (AUC), was reduced by 11% (90% CI: 6,16). These food effects were not considered to be of clinical significance. There was statistical evidence of nonproportionality in Cmax and AUC over the dose range 25,200 mg. However the degree of nonproportionality was small, with predicted increases in Cmax and AUC of 2.2- and 2.1-fold, respectively, for a doubling in dose, and was thought to be clinically nonsignificant. Sildenafil was well tolerated in the three studies; the majority of adverse events were mild and transient. Conclusions, Sildenafil had a mean absolute bioavailability of 41%. Food caused small reductions in the rate and extent of systemic exposure; these reductions are unlikely to be of clinical significance. Across the dose range of 25,200 mg, systemic exposure increased in a slightly greater than dose-proportional manner. [source] Cost Efficiency for Alberta and Ontario Dairy Farms: An Interregional ComparisonCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 2-3 2005Getu Hailu In this study, two non-homothetic translog stochastic meta-frontier cost functions,with and without local concavity imposed,are estimated using a nonlinear maximum likelihood estimation procedure to compare the cost efficiency of Alberta and Ontario dairy farms for the period 1984,96. The resulting cost efficiency estimates are not very sensitive to whether or not curvature is imposed. In contrast, the properties of the cost and input demand functions (e.g., elasticities) are sensitive to imposition of local concavity during estimation. The implication is that if an inappropriate model that does not satisfy the properties required by the economic theory is used, the estimated input demand functions may not be reliable. Average cost efficiency for the pooled sample, with local concavity imposed, is approximately 89%. This suggests some potential for improved performance in the sector. The results also suggest that Ontario dairy farms may be more cost efficient than Alberta dairy farms, but the statistical evidence is inconclusive. Dans la présente étude, nous avons estimé deux fonctions de coût métafrontières, stochastiques, non homothétiques de forme translogarithmique, avec et sans la concavité locale imposée, à l'aide de la procédure d'estimation du maximum de vraisemblance non linéaire pour comparer l'efficacité-coût des exploitations laitières de l'Alberta et de l'Ontario au cours de la période 1984,96. Les estimations des indices d'efficacité-coût ne sont pas très sensibles à l'imposition ou non de la concavité. En revanche, les propriétés des fonctions de coût et de demande d'intrants (ex. élasticités) sont sensibles à l'imposition de la concavité locale. La conséquence est que si on utilise un modèle incorrect qui ne respecte pas les propriétés requises par la théorie économique, les fonctions estimées de demande d'intrants peuvent ne pas être fiables. L'efficacité-coût moyen de l'échantillon total, avec la concavité locale imposée, est d'environ 89%. Ces résultats laissent supposer que certaines améliorations sont possibles dans le secteur. Ils laissent également supposer que les exploitations laitières de l'Ontario sont plus efficaces par rapport aux coûts que celles de l'Alberta, mais ces résultats ne sont pas statistiquement concluants. [source] Effect of familial history and smoking on common cancer risks in JapanCANCER, Issue 10 2007Takeshi Suzuki MD Abstract BACKGROUND Inherited genetic predispositions are important risk factors for the development of cancer in general. To determine genetic susceptibility for 14 common cancers, a case,control study of the impact of a family history of cancer in first-degree relatives was conducted. The authors further evaluated the effect modification by habitual smoking with adjustment for other confounding environmental factors. METHODS In total, 18,836 cancer cases and 28,125 age,matched and sex,matched controls, confirmed as being free of cancer, were recruited. Odds ratios (ORs) and 95% confidence intervals were determined by multiple logistic regression analysis, including stratification by family history for 14 cancer sites and interactions with a smoking history. RESULTS The associations between family history and risk of cancer were generally stronger at the same sites than across cancer sites. Risks to first-degree relatives at the same sites were found to be significantly elevated with 8 of 14 cancer sites; especially high ORs were found for prostate and thyroid cancers. Some across-site associations were observed; in particular, a reciprocal association between breast and prostate cancer was found. The interaction between family history and smoking history for breast cancer was found to be statistically significant. There was no statistical evidence for the interactions in other sites, but among subjects with a family history, the ORs were found to be higher in smokers compared with nonsmokers. CONCLUSIONS The results of the current study support the hypothesis of a genetic susceptibility to cancers in family members. For breast cancer, the interaction between family history and smoking history was observed to be significant. Cancer 2007. © 2007 American Cancer Society. [source] The meta-analysis of the Italian studies on short-term effects of air pollution (MISA): old and new issues on the interpretation of the statistical evidencesENVIRONMETRICS, Issue 3 2007Pierantonio Bellini Abstract The second meta-analysis of the Italian studies on short-term health effects of air pollution, known as MISA-2, was based on daily time series of indicators of both pollution and of health outcomes. It covered 15 cities during 1996,2002 for a total population of approximately nine millions. Health outcomes included mortality for natural causes, for respiratory diseases and for cardiovascular conditions, as well as hospital admissions for respiratory, cardiac and cerebrovascular diseases. Pollutants considered in univariate analyses were sulphur dioxide (SO2), nitrogen oxide (NO2), carbon monoxide (CO), suspended particulate matter (SPM) measuring less than 10,µm diameter (PM10) and ozone (O3, limited to the summer period). Results, including risk estimates, have been largely confirmatory of findings obtained in previous large meta-analytic studies carried out in North America and in Europe. A full report in Italian is available. The present contribution summarises the results of MISA-2 and addresses three major issues regarding their interpretation: robustness of the causal inferential process, the role of specific air pollutants and the reliability of risk estimates. The former issue is stressed according to Bradford Hill's criteria and the conclusion is reached that at least for the association of air pollution with an increase in mortality the evidence for causality is strong. Assessing the role of each air pollutant is problematic: there is some evidence that the effects of PM10 are partly confounded by other pollutants, but PM10 may not be the best indicator of the role of air SPM (routine measures of PM2.5 have not been introduced in Italy). As for risk estimates, the per cent increase in risk of mortality for unit increase in PM10 concentration, measured in MISA-2, is remarkably similar to estimates in other studies and there is indication for linearity of the dose,response relationship. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||