How to use χ2 test correctly—— χ2 test for the data of four-fold tables collected from the cohort design / 四川精神卫生

The purpose of this paper was to introduce the χ2 test for the data of four-fold tables collected from the cohort design， the hypothesis test and interval estimation of relative risk， and the implementation of SAS and R software. In view of the characteristics of cohort design， the concept of relative risk， hypothesis testing and interval estimation were emphasized. It was given that the interpretation of the results calculated by SAS and R software， as well as the statistical and professional conclusions.

How to use χ2 test correctly—— χ2 test for the data of four-fold tables collected from the case-control design / 四川精神卫生

The purpose of this paper was to introduce the χ2 test for the data of four-fold tables collected from the case-control design， the hypothesis test and interval estimation of odds ratio， and the implementation of SAS and R software. In view of the characteristics of case-control design， the concept of odds ratio， hypothesis testing and interval estimation were emphasized. It was given that the interpretation of the results calculated by SAS and R software， as well as the statistical conclusion and professional.

How to use χ2 test correctly——the analysis of common relative risk for the data of a multiway table and the implementation of SAS software / 四川精神卫生

The purpose of the paper was to introduce the relative risk analysis method of g×2×2 table data and the calculation method based on SAS software. The contents included the following aspects： firstly， the homogeneity test of the data in the g×2×2 table was performed； secondly， when the data met the homogeneity requirements， the point estimation and confidence interval estimation of the common relative risk based on the correction method were implemented； thirdly， when the data did not meet the requirements of homogeneity， the common relative risk RRDL and its 95% confidence interval were estimated， based on the DerSimonian-Laird method （DL method for short）； fourthly， when the data met and did not meet the requirements of homogeneity， the hypothesis of "whether the common relative risk equals to 1" was tested. Combining two examples and based on SAS software， the paper completed the following three tasks： ① the homogeneity test for the relative risk； ② the point estimation of the common relative risk； ③the confidence interval estimation of the common relative risk. The last two tasks were performed under the conditions of the data met and did not meet the homogeneity requirements， respectively. The output results of SAS software were explained， and the statistical and professional conclusions were made.

How to use χ2 test correctly——the analysis of common odds ratio for the data of a multiway table and the implementation of SAS software / 四川精神卫生

The purpose of this article was to introduce the odds ratio analysis method of g×2×2 table data and the calculation method based on SAS software. The contents included the following aspects： firstly， the homogeneity test of the odds ratio of the data in the g×2×2 table was performed； secondly， when the data met the homogeneity requirements， point estimation and confidence interval estimation for the common odds ratio based on the correction method were implemented； thirdly， when the data did not meet the homogeneity requirements， based on the approach of "the conditional distribution of the frequency in the （1，1） grid in each layer 2×2 table" ， these things， such as the point estimation and confident interval estimation as well as hypothesis testing about the common odds ratio， were accurately estimated and performed. All calculations were realized based on the FREQ procedure in SAS/STAT by means of two real examples. Furthermore， the output results of SAS software were explained， and the statistical and professional conclusions were made.

How to use χ2 test correctly——the rate ratio analysis for the data of the person-time and the implementation of SAS software / 四川精神卫生

The purpose of this paper was to introduce the methods of the "layered person-time data" rate ratio analysis and the SAS implementation. The specific contents included the following four aspects： ① the point estimation and the confidence interval estimation of the layer i rate ratio in the stratified person-time data； ② the homogeneity test of the rate ratios among the different layers； ③ the point estimation and the confidence interval estimation of the common rate ratio； ④ the linear trend test of the incidence density in the stratified person-time data. Through two examples， it showed the statistical calculation process based on the SAS software to realize the aforementioned four kinds of the analysis contents， including providing the SAS program code， the explanation of the SAS output results， and giving the statistical and professional conclusions.

How to use χ2 test correctly——the analysis of a common risk difference for the data of a multiway table and the implementation of SAS software / 四川精神卫生

The purpose of this article was to introduce the risk rate difference analysis method of the g×2×2 table data and the calculation method based on the SAS software. The tasks that needed to be completed included the following two terms： first， the point estimation of the common risk rate difference and its confidence interval estimation； second， the test "whether the common risk rate difference was equal to 0". Among them， there were a total of 6 approaches for achieving the aforementioned first task； and three approaches for achieving the aforementioned second task. Based on the SAS software and an example， the article realized the point estimation， the confidence interval estimation and the hypothesis test of the common risk rate difference， respectively. Next， the SAS output results were explained and the statistical and professional conclusions were made.

Hepatotoxicity reports in the FDA adverse event reporting system database: A comparison of drugs that cause injury

Drug-induced liver injury (DILI) is a leading reason for preclinical safety attrition and post-market drug withdrawals. Drug-induced mitochondrial toxicity has been shown to play an essential role in various forms of DILI, especially in idiosyncratic liver injury. This study examined liver injury reports submitted to the Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) for drugs associated with hepatotoxicity

Intervalo de confianza para el porcentaje poblacional de profesores con categoría docente Asistente / Confidence interval for the percent of teaching population with category of Teaching Assistant

RESUMEN En el proceso de autoevaluación de las carreras de Estomatología y Medicina para su acreditación en la Universidad de Ciencias Médicas de Matanzas en Cuba, dentro de la variable profesores se señala como una debilidad de los claustros docentes, el no predominio de las categorías principales titular y auxiliar, con un grupo de profesores mayoritariamente en la categoría de asistente, lo que motivó que se realizara la estimación de un intervalo de confianza para el verdadero valor del porcentaje de profesores con categoría asistente en el claustro de la Universidad con el objetivo de opinar basado en un método sólido y sencillo el rango de valores donde posiblemente se encuentre el valor real, utilizando las fórmulas del intervalo estándar y el de Wilson (AU).

SUMMARY The non-predominance of the main categories of Main Professor and Lecturer, with a group of professors mostly in the category of Assistant was pointed out in the variable Teachers, as weakness of the faculties in the auto evaluation process of Stomatology and Medicine undergraduate studies for their accreditation in the University of Medical Sciences of Matanzas in Cuba; it motivated the estimation of a confidence interval for the true value of the percent of teachers with category of Assistant in the University staff with the aim of holding a position based on a solid and simple method, on the rank of values where possibly is the real value, using the standard and Wilson´s interval formula (AU).

Pharmacokinetic Characteristics of Oral Hydroxysafflor Yellow A in Rats / 中国药学杂志

OBJECTIVE: To investigate the linear pharmacokinetics characteristics of hydroxysafflor yellow A (HSYA) in rats at different doses. METHODS: Eighteen male SD rats were randomly divided into three groups. HSYA was administered intragastrically at doses of 30, 60 and 120 mg•kg-1 respectively. The blood samples were collected from rat fundus venous plexus at preset time points. The blood concentration of HSYA was determined by HPLC. The pharmacokinetic characteristics of HSYA in rats were analyzed by descriptive method and confidence interval method. RESULTS: There were no dose dependence of non-atrioventricular and atrioventricular pharmacokinetic parameters clearance (CL), which were about 6 L•h-1•kg-1. The area under concentration-time curve (AUC) and peak concentration (ρmax) were correlated with the dosage of HSYA. CONCLUSION: The pharmacokinetic parameters AUC of HSYA in the dose range of 30-120 mg•kg-1 have linear kinetic characteristics.

Clinical Application of Overlapping Confidence Intervals for Monitoring Changes in Serial Clinical Chemistry Test Results

BACKGROUND: Interpretation of changes in serial laboratory results is necessary for both clinicians and laboratories; however, setting decision limits is not easy. Although the reference change value (RCV) has been widely used for auto-verification, it has limitations in clinical settings. We introduce the concept of overlapping confidence intervals (CIs) to determine whether the changes are statistically significant in clinical chemistry laboratory test results.METHODS: In total, 1,202,096 paired results for 33 analytes routinely tested in our clinical chemistry laboratory were analyzed. The distributions of delta% absolute values and cut-off values for certain percentiles were calculated. The CIs for each analyte were set based on biological variation, and data were analyzed at various confidence levels. Additionally, we analyzed the data using RCVs and compared their clinical utility.RESULTS: Most analytes had low indexes of individuality with large inter-individual variability. The 97.5th percentile cut-offs for each analyte were much larger than conventional RCVs. The percentages of results exceeding RCV(95%) and RCV(99%) corresponded to those with no overlap at the 83.4% and 93.2% confidence levels, respectively.CONCLUSIONS: The use of overlapping CIs in serial clinical chemistry test results can overcome the limitations of existing RCVs and replace them, especially for analytes with large intra-individual variation.

Conceptos generales en bioestadística y epidemiología clínica: error aleatorio y error sistemático / General concepts in biostatistics and clinical epidemiology: random error and systematic error

La investigación biomédica, particularmente la que involucra a seres humanos, está siempre sometida a fuentes de error que deben ser reconocidas. El error sistemático o sesgo, se asocia con debilidades en el diseño metodológico o de la fase de ejecución del estudio. Éste afecta su validez y se valora cualitativamente. Por su parte, el error aleatorio se relaciona con las variaciones producidas por el azar, el cual puede expresarse cuantitativamente, pero nunca eliminarse. Esta revisión es la primera entrega de una serie metodológica sobre conceptos generales en bioestadística y epidemiología clínica desarrollada por la Cátedra de Metodología de la Investigación Científica de la Universidad de Valparaíso, Chile. En este artículo se abordan los conceptos teóricos asociados al error, su evaluación y control. Finalmente, se discuten algunas controversias actuales en cuanto a su conceptualización, de relevancia para estudiantes de pre y posgrado de ciencias de la salud.

Biomedical research, particularly when it involves human beings, is always subjected to sources of error that must be recognized. Systematic error or bias is associated with problems in the methodological design or during the execu-tion phase of a research project. It affects its validity and is qualitatively ap-praised. On the other hand, random error is related to variations due to chance. It may be quantitatively expressed, but never removed. This review is the first of a methodological series on general concepts in biostatistics and clin-ical epidemiology developed by the Chair of Scientific Research Methodology at the School of Medicine, University of Valparaíso, Chile. In this article, we address the theoretical concepts of error, its evaluation, and control. Finally, we discuss some current controversies in its conceptualization that are relevant to undergraduate and graduate students of health sciences.

Intervalo de confianza para las normas del cefalograma resumido de Ricketts en niños de cubanos / Confidence interval for the standards of the Ricketts´summarized cephalogram in Cuban children

Introducción: en hallazgos cefalométricos de diferentes países en poblaciones con patrones de crecimientos y oclusión normal, se reportan diferencias estadísticamente significativas a los valores dados en los cefalogramas de Ricketts, Steiner, Downs, Jarabak y otros. En Cuba no existen estudios de estos patrones en niños con dentición mixta los que favorecerían un mejor diagnóstico de las anomalías dento-maxilofaciales. Objetivo: proponer el perfeccionamiento de las normas del cefalograma resumido de Ricketts para los niños. Materiales y Métodos: investigación observacional, descriptiva en cuatro poblaciones pertenecientes a las siguientes zonas del país: Matanzas, Cárdenas, Camagüey y Sancti Spíritus. El universo estuvo constituido por 1 657 niños de 9 años de edad. La muestra 163 niños, seleccionados por el método estratificado por conglomerados con oclusión dentaria normal. Se utilizó el análisis del cefalograma resumido de Ricketts y la prueba t de media para determinar los valores de las variables estudiadas y se hicieron estimaciones puntuales y por intervalos de confianza. Resultados: tres variables mostraron medias iguales a las normas de Ricketts: eje facial (90°), profundidad facial (87°) y profundidad maxilar (90°). En las restantes fueron comprobadas diferencias significativas. Se obtuvo un intervalo de confianza para cada una de las variables del cefalograma resumido de Ricketts. Conclusiones: solamente tres variables presentaron valores similares a los planteados por Ricketts, las restantes presentaron valores que difieren significativamente de los planteados por Ricketts. Se propone utilizar el intervalo de confianza obtenido en esta investigación en las variables del cefalograma resumido de Ricketts para diagnosticar las anomalías dento-maxilofaciales en niños cubanos (AU).

Introduction: in cephalometric findings from different countries in populations with normal growing and occlusion patterns, significant statistic differences are reported in relation to the values given in the cephalograms of Ricketts, Steiner, Downs, Jarabak, and others. In Cuba there are not studies of these patterns in children with mixed dentition that might allow a better diagnosis of dental, maxilla-facial anomalies. Objective: to propose the improvement of the standards of the Ricketts abridge cephalogram for children. Materials and methods: descriptive, observational research in four populations belonging to different regions of the country: Matanzas, Cárdenas, Camagüey and Sancti Spíritus. The universe was formed by 1675 children aged 9 years old; the sample, 163 children with normal dental occlusion, was chosen by the stratified method per conglomerate. The analysis of the Ricketts summarized cephalogram and the mean T test were used to determine the values of the studied variables; punctual estimates and estimates by confidence interval were carried out. Results: three variables showed equal means than Ricketts' standards: facial axis (90o), facial depth (87o) and maxillary depth (90o). In the remaining variables there were found significant differences. A confidence interval was obtained for every one of the Ricketts' summarized cephalogram variable. Conclusions: only three variables showed values similar to those given by Ricketts. The remaining ones presented values significantly differing from those established by Ricketts. The proposition is using the confidence interval obtained in this research in the variables of the Ricketts' summarized cephalogram to diagnose the dental-maxillafacial anomalies in Cuban children (AU).

Essentials of Statistics in Dental Research: Part 1.

Dental professionals review articles in scientific dental journals to be informed about progress in the field and to remain up to date in the dental literature. As a general rule, knowing the basic statistical concepts such as study design, hypothesis testing, confidence interval, significance level, effect size, and sample size and power can help readers to better understand the whole concept of an article. Reviews of statistical methodology in published papers of well-established dental journals concluded that the majority of the papers contained statistical errors. Inappropriate use of statistical methods may lead to incorrect conclusions and a waste of valuable resources. The aim of this paper is to provide an overview on some implications of the statistical concepts and recommendations for avoiding statistical errors in dental research.

Pharmacokinetic study of salvianolic acid D after oral and intravenous administration in rats

A sensitive, specific and rapid LC-MS method was developed and validated for the determination of salvianolic acid D (SalD) in rat plasma. This method used a single quadrupole mass spectrometer with an electrospray ionization (ESI) source. A single ion monitoring scanning (SIM) mode was employed. It showed good linearity over the concentration range from 3.3 to 666.7 ng/mL for the determination of SalD. The R.S.D.% of intra-day and inter-day precision values were no more than 7.69%, and the accuracy was within 91%-104% at all quality control levels. This LC-MS method was applied to the pharmacokinetic study of SalD in rats. A two-compartmental model analysis was employed. The plasma concentrations at 2 min (C 2min) were 5756.06±719.61, 11,073.01±1783.46 and 21,077.58±5581.97 μg/L for 0.25, 0.5 and 1 mg/kg intravenous injection, respectively. The peak plasma concentration (C max) was 333.08±61.21 μg/L for 4 mg/kg oral administration. The area under curve (AUC0-t ) was 14,384.379±8443.184, 22,813.369±11,860.823, 46,406.122±27,592.645 and 8201.740±4711.961 μg/L·h for intravenous injection (0.25, 0.5 and 1 mg/kg) and oral administration (4 mg/kg), respectively. The bioavailability of SalD was calculated to be 4.159%±0.517%.

Test-Retest Reliability of Word Recognition Score Using Korean Standard Monosyllabic Word Lists for Adults as a Function of the Number of Test Words

BACKGROUND AND OBJECTIVES: The purpose was to establish the test-retest reliability of word recognition score (WRS) using Korean standard monosyllabic word lists for adults (KS-MWL-A) recently developed based on the international standard for speech audiometry (ISO 8253-3:2012). SUBJECTS AND METHODS: Subjects consisted of 159 adults aged to 18 to 25 years with normal hearing sensitivity. WRSs were obtained in 2 dB steps from the level of speech recognition thresholds to the level of 86% correct responses or greater. After one or two weeks, retest was performed. Correlation, confidence interval (CI) and prediction interval (PI) were calculated for the reliability. RESULTS: Correlation coefficients were 0.88 for 50 test words, 0.76 for 25 and 0.61 for 10 words. Results also showed that 95% CIs and PIs were narrower for 25 and 50 test words than those for 10 test words. CONCLUSIONS: Korean WRS using the KS-MWL-A has high reliability for 25 and 50 test words, but relatively low for 10 words. It suggested that 95% CIs for each test words would be criteria for significant differences in WRS for groups and 95% PIs at each score of WRS could be utilized for a considerable difference for each individual at retest.

Validation of models with constant bias: an applied approach / Validación de modelos con sesgo constante: un enfoque aplicado

Objective. This paper presents extensions to the statistical validation method based on the procedure of Freese when a model shows constant bias (CB) in its predictions and illustrate the method with data from a new mechanistic model that predict weight gain in cattle. Materials and methods. The extensions were the hypothesis tests and maximum anticipated error for the alternative approach, and the confidence interval for a quantile of the distribution of errors. Results. The model evaluated showed CB, once the CB is removed and with a confidence level of 95%, the magnitude of the error does not exceed 0.575 kg. Therefore, the validated model can be used to predict the daily weight gain of cattle, although it will require an adjustment in its structure based on the presence of CB to increase the accuracy of its forecasts. Conclusions. The confidence interval for the 1-α quantile of the distribution of errors after correcting the constant bias, allows determining the top limit for the magnitude of the error of prediction and use it to evaluate the evolution of the model in the forecasting of the system. The confidence interval approach to validate a model is more informative than the hypothesis tests for the same purpose.

Objetivo. Presentar extensiones al método estadístico para validar modelos basado en el procedimiento de Freese cuando el modelo presenta sesgo constante (SC) en sus predicciones e ilustrar el método con datos provenientes de un modelo mecanístico inédito para la predicción de ganancia de peso de bovinos. Materiales y métodos. Las extensiones fueron la prueba de hipótesis y error máximo anticipado para el planteamiento alternativo y el intervalo de confianza para un cuantil de la distribución de los errores. Resultados. El modelo evaluado presentó SC, una vez eliminado y con un nivel de confianza del 95%, la magnitud del error no sobrepasa 0.575 kg. Por lo que el modelo validado puede usarse para predecir la ganancia de peso diaria de bovinos, aunque requerirá un ajuste en su estructura con base a la presencia de SC para incrementar la exactitud en sus pronósticos. Conclusiones. El intervalo de confianza para el cuantil 1-α de la distribución de los errores una vez que se corrige el sesgo constante, permite determinar una cota superior para la magnitud del error de predicción y usarla para evaluar la evolución del modelo en predicción del sistema. El enfoque de intervalos de confianza para validar un modelo es más informativo que las pruebas de hipótesis para el mismo propósito.

Non-parametric Bootstrap estimation on the intraclass correlation coefficient generated from quantitative hierarchical data / 中华流行病学杂志

This paper aims to achieve Bootstraping in hierarchical data and to provide a method for the estimation on confidence interval (CI) of intraclass correlation coefficient (ICC).First,we utilize the mixed-effects model to estimate data from ICC of repeated measurement and from the two-stage sampling.Then,we use Bootstrap method to estimate CI from related ICCs.Finally,the influences of different Bootstraping strategies to ICC' s CIs are compared.The repeated measurement instance show that the CI of cluster Bootsraping containing the true ICC value.However,when ignoring the hierarchy characteristics of data,the random Bootsraping method shows that it has the invalid CI.Result from the two-stage instance shows that bias obsered between cluster Bootstraping's ICC means while the ICC of the original sample is the smallest,but with wide CI.It is necessary to consider the structure of data as important,when hierarchical data is being resampled.Bootstrapping seems to be better on the higher than that on lower levels.

Sample size: from formulae to concepts.

Sample size can be calculated from many online calculators or tables. But the use of these instruments is rational only when we understand our input data and the concept behind them completely. Terminologies like confidence interval, confidence limit, standard error of mean, margin of error, standard normal variate, power, significance level etc. and extent to which population size or chances of occurrence of an outcome can affect our sample size remain to be well understood before using these software solutions.

Número de anos para a estimação da média decendial de duração diária do brilho solar no Rio Grande do Sul / Number of years to estimate the ten-day average of daily sunshine duration in Rio Grande do Sul State, Brazil

O objetivo deste trabalho foi determinar o tamanho de amostra (número de anos) para a estimação da média decendial de duração diária de brilho solar em 30 locais do Rio Grande do Sul. Com os dados de duração de brilho solar do período de 1960 a 2007, formaram-se 1.080 séries temporais (30 locais x 36 decêndios) de média decendial de duração diária de brilho solar. Testou-se a aleatoriedade e a normalidade dos dados, de cada série temporal, por meio dos testes de sequência (run test) e de Lilliefors, respectivamente. Para cada decêndio e local, foi determinado o tamanho de amostra por meio de reamostragem bootstrap, com reposição de 3.000 amostras. Vinte e cinco anos de observações são suficientes para a estimação da média decendial de duração diária de brilho solar, com amplitude do intervalo de confiança de bootstrap de 95% igual a 2,00 horas dia-1.

The objective of this research was to determine the sample size (number of years) to estimate the ten-day average of daily sunshine duration in 30 locations of the Rio Grande do Sul State, Brazil. With sunshine data duration of the period from 1960 to 2007, 1,080 time series (30 locations x 36 ten-days) of ten-day of daily sunshine duration average were formed. The aleatory and normality, in each time series, was verified through the run test and Lilliefors test, respectively. For each ten-day and locality, it was determined the sample size using bootstrap resampling with replacement of 3,000 samples. Twenty-five years of data are enough to predict the ten-day average of daily sunshine duration, with amplitude of bootstrap confidence interval of 95%, equal to 2.00 hour day-1.

Diâmetro do trado e número de amostras para quantificação do banco de sementes de arroz-vermelho do solo / Core diameter and number of samples to estimative the red rice seed bank

Com o objetivo de determinar o diâmetro ideal do trado e o número de amostras necessárias para quantificar o banco de sementes de arroz-vermelho, foram realizados levantamentos em lavouras de arroz irrigado, no Município de Santa Maria, Rio Grande do Sul (RS), Brasil. O experimento foi conduzido em três áreas de 400m² (20x20m), com diferentes níveis de infestação, sendo considerado nível baixo, médio e alto, respectivamente, 71, 282 e 498 sementes de arroz-vermelho por m², coletadas com trados de 5, 10 e 15cm de diâmetro. Os resultados mostraram que, quanto maior o diâmetro do trado, menor foi o CV entre as amostras. O trado com 10cm de diâmetro foi mais funcional e necessitou de 280, 55 e 31 (D=20 por cento); 33, nove e seis (D=60 por cento); e 13, quatro e três (D=100 por cento) amostras de solo, respectivamente, para as infestações de 71, 282 e 498 sementes de arroz-vermelho por m². O número de amostras de solo necessário para melhor estimar populações de sementes de arroz-vermelho é variável com o número médio de sementes no solo e com a precisão desejada.

Aiming to estimate the number of samples, and the diameter of soil sampler ideal for red rice infestation level, a irrigated rice field survey has been conducted in Santa Maria, Rio Grande do Sul (RS), Brazil, The experiment was conducted in three areas with 400m² (20x20m) with different red rice infestation levels considering low, medium and high infestation levels with 71, 282 and 498 red rice seeds per m², respectively, sample with 5, 10 and 15cm core diameter. The results showed that with larger core diameter the samples coefficient variation among samples was smaller. The core of 10 cm is more functional, been necessary 280, 55 and 31 (D=20 percent), 33, 9 and 6 (D=60 percent) and 13, 4 and 3 (D=100 percent) soil samples for the infestation levels 71, 282 and 498 red rice seeds per m² respectively. The number of soil samples necessary to estimate the red rice seed bank is variable with the infestation level and the desirable precision.