Standard Error

Os modelos polinomiais são mais difundidos no meio florestal brasileiro na descrição do perfil de árvores devido à sua facilidade de ajuste e precisão. O mesmo não ocorre com os modelos não-lineares, os quais possuem maior dificuldade de ajuste. Dentre os modelos não-lineares clássicos, na descrição do perfil, podem-se citar o de Gompertz, o Logístico e o de Weibull. Portanto, este estudo visou comparar os modelos lineares e não lineares para a descrição do perfil de árvores. As medidas de comparação foram o coeficiente de determinação (R²), o erro-padrão residual (s yx), o coeficiente de determinação corrigido (R²ajustado), o gráfico dos resíduos e a facilidade de ajuste. Os resultados ressaltaram que, dentre os modelos não-lineares, o que obteve melhor desempenho, de forma geral, foi o modelo Logístico, apesar de o modelo de Gompertz ser melhor em termos de erro-padrão residual. Nos modelos lineares, o polinômio proposto por Pires & Calegario foi superior aos demais. Ao comparar o...

Mixture modeling within the context of pharmacokinetic (PK)/pharmacodynamic (PD) mixed effects modeling is a useful tool to explore a population for the presence of two or more subpopulations, not explained by evaluated covariates. At present, statistical tests for the existence of mixed populations have not been developed. Therefore, a simulation study was undertaken to evaluate mixture modeling with NONMEM and explore the following questions. First, what is the probability of concluding that a mixed population exists when there truly is not a mixture (false positive significance level)? Second, what is the probability of concluding that a mixed population (two subpopulations) exists when there is truly a mixed population (power), and how well can the mixture be estimated, both in terms of the population parameters and the individual subject classification. Seizure count data were simulated using a Poisson distribution such that each subject's count could decrease from its baseline value, as a function of dose via an Emax model. The dosing design for the simulation was based on a trial with the investigational anti-epileptic drug pregabalin. Four hundred and forty seven subjects received pregabalin as add on therapy for partial seizures, each with a baseline seizure count and up to three subsequent seizure counts. For the mixtures, the two subpopulations were simulated to differ in their Emax values and relative proportions. One subpopulation always had its Emax set to unity (Emax hi), allowing the count to approach zero with increasing dose. The other subpopulation was allowed to vary in its Emax value (Emax lo=0.75, 0.5, 0.25, and 0) and in its relative proportion (pr) of the population (pr=0.05, 0.10, 0.25, and 0.50) giving a total of 4 ⋅ 4=16 different mixtures explored. Three hundred data sets were simulated for each scenario and estimations performed using NONMEM. Metrics used information about the parameter estimates, their standard errors (SE), the difference between minimum objective function (MOF) values for mixture and non-mixture models (MOF(δ)), the proportion of subjects classified correctly, and the estimated conditional probabilities of a subject being simulated as having Emax lo (Emax hi) given that they were estimated as having Emaxlo (Emax hi) and being estimated as having Emaxlo (Emax hi) given that they were simulated as having Emax lo (Emax hi). The false positive significance level was approximately 0.04 (using all 300 runs) or 0.078 (using only those runs with a successful covariance step), when there was no mixture. When simulating mixed data and for those characterizations with successful estimation and covariance steps, the median (range) percentage of 95% confidence intervals containing the true values for the parameters defining the mixture were 94% (89–96%), 89.5% (58–96%), and 95% (92–97%) for pr, Emax lo, and Emax hi, respectively. The median value of the estimated parameters pr, Emax lo (excluding the case when Emax lo was simulated to equal 0) and Emax hi within a scenario were within ±28% of the true values. The median proportion of subjects classified correctly ranged from 0.59 to 0.96. In conclusion, when no mixture was present the false positive probability was less than 0.078 and when mixtures were present they were characterized with varying degrees of success, depending on the nature of the mixture. When the difference between subpopulations was greater (as Emax lo approached zero or pr approached 0.5) the mixtures became easier to characterize.

Aerosols have been shown to affect the quantity and quality of solar radiation on the Earth’s surface. Savanna regions are subject to frequent burning and release of aerosols that may impact on radiation components and possibly vegetation productivity in this region. Therefore, in this study, we have analyzed the optical properties of aerosols (aerosol optical depth (AOD) and Angstrom coefficient) from the Atmospheric Radiation Measurement site in Darwin for the periods from April 2002 to June 2005 as measured by a multifilter rotating shadowband radiometer. The influence of aerosols and their effect on surface shortwave incoming solar radiation and savanna productivity were examined for the dry season using sky radiation collection of radiometers and eddy covariance measurements from the Howard Springs flux site. Results indicated that aerosol concentrations in the region were relatively low compared to other savanna regions with the maximum monthly average AOD over the period being the greatest in October (0.29 ± 0.003 standard error at 500 nm). The highest monthly average Angstrom exponent was also found in October (1.38 ± 0.008). The relatively low aerosol concentration in this region can be attributed to the mixture of smoke aerosols with humidity haze and local circulations. Over a range of AODs from 0.1 to 0.4, we found a modest increase in the fraction of diffuse radiation to total radiation from 11% to 21%. This small increase in diffuse fraction did not affect the carbon flux significantly. However, because the current range of AOD in the region is relatively low, the region could be sensitive to increases in aerosols and diffuse fraction in the future.

Leaf thickness plays an important role in leaf and plant functioning, and relates to a species' strategy of resource acquisition and use. As such, it has been widely used for screening purposes in crop science and community ecology. However, since its measurement is not straightforward, a number of estimates have been proposed. Here, the validity of the (SLA x LDMC)(-1) product is tested to estimate leaf thickness, where SLA is the specific leaf area (leaf area/dry mass) and LDMC is the leaf dry matter content (leaf dry mass/fresh mass). SLA and LDMC are two leaf traits that are both more easily measurable and often reported in the literature. The relationship between leaf thickness (LT) and (SLA x LDMC)(-1) was tested in two analyses of covariance using 11 datasets (three original and eight published) for a total number of 1039 data points, corresponding to a wide range of growth forms growing in contrasted environments in four continents. The overall slope and intercept of the...

hoi computes the Human Opportunity Index proposed by Barros et al (2008), including the Coverage of Basic Opportunities (P), the Dissimilarity Index (D), and the Human Opportunity Index (HOI). Analytical standard errors are reported for the P, D, and HOI. The program also computes two decompositions of changes of the HOI: (i) the scale and distribution decomposition Barros et al

Objective: Calibration with LC-MS data may be accomplished with different combinations of curve fit, weighting, and origin treatment. Agilent's Mass Hunter Quantitative Analysis software contains a Curve Fit Assistant, which allows comparison of over 100 different calibration options. Curve fit choices include linear, quadratic, power, logarithmic, second order logarithmic, and average of response factors. Weighting choices include equal, inverse x

The best known indicator of risk for first bleeding in patients with cirrhosis without previous bleeding is the index devised by the North Italian Endoscopic Club for the Study and Treatment of Esophageal Varices (NIEC index), which results from the combination of size of esophageal varices, severity of red wale marks, and Child-Pugh class. Its efficiency is far from optimal, and validation studies have reported sensitivities and specificities markedly lower than those reported in the original study. In the present study we analyzed the efficiency of NIEC index in a large series of cirrhotic patients with varices without previous bleeding. In addition, we tried to improve the effectiveness of the index by modifying it, and to validate the modifications in an independent group of patients.

Water table across much of the western Victoria, Australia have been declining for at least the last 10-15 years, and this is attributed to the consistently low rainfall for these years, but over the same period of time there has been substantial change in land use, with grazing land replaced by cropping and tree plantations appearing in some areas. Hence,

The practice for selection of earthquake ground motion for design of large dams as recommended by the International Committee on Large Dams (ICOLD) bulletin 72 is examined. It is shown that the recommended practice is flawed and does not bear a scrutiny on the basis of statistical theory. The ground motion attenuation relationships are derived on the basis of different sets of assumptions and different sets of data, and with different standard errors. Estimates from these different attenuation relationships cannot be ...

The main aim of this paper is to present a new method of areal rainfall estimation using satellite and ground-based data. This method involves optimal merging of the estimates provided by satellite information and estimates obtained from raingauges. In the merging procedure, each estimate is weighted according to its uncertainty given by its estimation variance. The uncertainty attributed to the raingauge estimates is obtained using block kriging, while for the satellite uncertainties, a novel regression approach is developed. A standard error is also attached to the new merged estimates. In order to test the algorithm, a case study has been undertaken using the EPSAT dense raingauge network in Niger. The complete EPSAT raingauge network (94 gauges distributed over a 1×1° square) has been used to obtain a detailed picture of the rainfall pattern which is then used as a reference for comparing the estimation schemes. The schemes compared are: (1) estimates based on satellite data only; (2) kriged estimates from a randomly selected subset of four gauges; (3) kriging with external drift using both satellite data and the subset of gauges; and (4) the new merging algorithm. The merging process gives more reliable results both for the mean areal rainfall and its spatial distribution.

Background: Scaling and root planing (SRP) are the bases of non-surgical therapy in the treatment of periodontitis. However, results from this therapy are often unpredictable and dependable from many different factors. Objectives: The aim of this systematic review was ...

Abstrak Standar eror adalah standar deviasi ketepatan dalam mengukur nilai mean atau nilai rata-rata sehingga keakuratan yang diinginkan oleh seorang peneliti dapat mengidentifikasikan ukuran yang digunakan statistik sampel untuk menduga parameter populasi. Adapun cara penulisan yang digunakan menggunakan SE (standar error estiminasi statistik). Eror penyimpanan dibagi menjadi dua bagian yaitu sampling eror dan non sampling eror. A. Pengertian Standar eror merupakan nilai yang mengukur ketepatan nilai mean yang diperoleh atau ketepatan nilai mean yang diperoleh dibandingkan dengan nilai mean keseluruhan data populasi. Standar eror bisa juga disebut standar kesalahan mean. Secara sederhana, standar eror diartikan sebagai standar deviasi dari rata-rata sampel (Tri, Cahyono, SKM., 2018, p. 98). Standar deviasi distribusi mean sampel digunakan untuk menjelaskan satu distribusi mean sampel yaitu statistik yang merujuk pada standar eror mean (Fred L Benu & Prof, 2019, p. 122). Standar deviasi dari distribusi statistik sampel dikenal sebagai standar eror dari statistik. Standar eror yang diterapkan menyangkut keakuratan yang diinginkan oleh seorang peneliti mengidentifikasikan ukuran yang digunakan statistik sampel untuk menduga parameter populasi. Standar eror dari mean dari distribusi mean