ABSTRACT
Statistics is the study of the collection, organization, analysis, interpretation and presentation of data. It deals with all aspects of data. It is usually noticed that some routine words are given technical meanings in statistical parlance (e.g. “mean,” “normal,” “significance,” “effect,” and “power”). It is essential to resist the temptation of conflating their technical meanings. A failure to do so may have a lot to do with the ready acceptance of the “effect size” and “power” arguments in recent years. As, statistics is used (i) to describe data in terms of the shape, central tendency, and dispersion of their simple frequency distribution, and (ii) to make decisions about the properties of the statistical populations on the basis of sample statistics. Statistical decisions are made with reference to a body of theoretical distributions: the distributions of various test statistics that are in turn derived from the appropriate sample statistics. In every case, the calculated test statistic is compared to the theoretical distribution, which is made up of an infinite number of tokens of the test statistic in question. Hence, the “in the long run” caution should be made explicit in every probabilistic statement based on inferential statistics (e.g. “the result is significant at the 0.05 level in the long run”).Despite the recent movement to discourage psychologists from conducting significance tests, significance tests can be defended by (i) clarifying some concepts, (ii) examining the role of statistics in empirical research, and (iii) showing that the sampling distribution of the test statistic is both the bridge between descriptive and inferential statistics and the probability foundation of significance tests. The present paper discusses the critical issues of statistics in psychological research.
ABSTRACT
O planejamento de atividades agropecuárias exige que os riscos climáticos, em um determinado local e período do ano, sejam estimados com máxima precisão. Dessa forma, foram utilizados os dados de 15 locais do Estado do Rio Grande do Sul, com o objetivo de estudar a variabilidade temporal e espacial da precisão das estimativas das médias mensais de precipitação pluvial, insolação, radiação solar global e temperaturas mínima, média e máxima. Para isso, calculouseo erro de estimação (semiamplitude do intervalo de confiança) (EE), em percentagem da estimativa da média mensal de precipitação pluvial, insolação, radiação solar global e temperaturas mínima, média e máxima, para cada mês e local, que foi utilizado como medida de precisão. A partir do EE, para cada um dos elementos meteorológicos, agruparam-se os meses e os locais, por meio do método hierárquico de Ward, e calculou-se o coeficiente de correlação linear de Pearson entre as matrizes de distância euclidiana média padronizada e gráfica a fim de verificar a consistência dos agrupamentos. Conclui-se que a precisão das estimativas, média de meses e locais, entre os elementos meteorológicos, aumenta na seguinte ordem: precipitação pluvial (EE=21,66%), insolação (EE=6,74%), radiação solar global (EE=5,52%) e temperaturas mínima (EE=4,40%), média (EE=2,63%) e máxima (EE=2,27%). Há variabilidade da precisão das estimativas das médias mensais de precipitação pluvial, insolação, radiação solar global e temperaturas mínima, média e máxima, no Estado do Rio Grande do Sul, no tempo (meses) e no espaço (locais). Estimativas com base em 30 anos de observações têm precisão menor nos meses de abril, maio, junho, julho, agosto e setembro, em relação aos demais meses.
Planning agricultural activities requires that climatic risks in each location and time of year are estimated with maximum precision. In this estudy data from15 locations of Rio Grande do Sul, Brazil, were used with the objective ofstuding spatial and temporal variability of the precision estimates average of monthly rainfall, sunshine, solar radiation global and temperatures minimum, mean and maximum. It was estimated the estimation error (half-amplitude of the confidence interval) (EE) in percentage of estimate averagemonthly rainfall, sunshine, solar radiation global and temperatures minimum, mean and maximum for each month and location, which was used as a measure of precision. From the EE, for each meteorological elements, months and locations were clustered by hierarchical method of Ward. The Pearsons linear correlation coefficient between the arrays of the standardized average euclidian distance and graphics was calculated in order to check the clusters consistency. It was concluded that the precision estimates, average of months and locations, between the meteorological elements, increases inthe following order: rainfall (EE=21.66%), sunshine (EE=6.74%), global solar radiation (EE=5.52%) andtemperatures minimum (EE=4.40%), mean (EE=2.63%) and maximum (EE=2.27%). Results showed that there is variability in precision estimate of monthly average rainfall, sunshine, global solar radiation and minimum, mean and maximum temperatures in Rio Grande do Sul, both in temporal and spatial scale. Estimates based on 30 years data are less precision in April, May, June, July, August and September in relation to the others.
ABSTRACT
Com o objetivo de verificar a variabilidade temporal e espacial do tamanho de amostra da radiação solar global média decendial, de 22 locais do Estado do Rio Grande do Sul, utilizaram-se séries de dados de radiação solar global do período de 1956 a 2003. Determinou-se o tamanho de amostra da radiação solar global média decendial em cada decêndio e local e agruparam-se os decêndios e os locais pelo método hierárquico 'vizinho mais distante'. Há variabilidade do tamanho de amostra (número de anos) para a estimativa da radiação solar global média decendial no Estado do Rio Grande do Sul no tempo e no espaço. Maior tamanho é necessário nos decêndios dos meses de junho, julho, agosto e setembro em relação aos outros meses. Para os locais e decêndios estudados, 30 anos de observações são suficientes para estimar a média (µ) de radiação solar global média decendial, para um erro de estimação igual a 12.3 por cento, com coeficiente de confiança de 95 por cento.
With the aim of verifying the temporal and spatial variability of the sample size ten-day average of the global solar radiation of 22 locations of Rio Grande do Sul State, Brazil, the global solar radiation data were collected from 1956 to 2003. One determined the sample size in each ten-day and location by clustering it using the complete linkage method. Results show that there is variability in the sample size of the ten-day average global solar radiation in Rio Grande do Sul State both in temporal and spatial scale. Greater sample size is necessary in the ten-day of June, July, August and September in relation to the others. For the studied locations and ten-day, 30 years of data are enough to predict the global solar radiation average (µ), for an error estimation equal to 12.3 percent average interval, with a reliable degree of 95 percent.
ABSTRACT
PURPOSE: The purpose of this study is to assess the validity and to review the errors of each category of inferential statistics used in Journal of Korean Ophthalmology Society (JKOS). METHODS: We reviewed 46 original articles of Journal of Korean Ophthalmology Society from January 2000 to March 2000 to assess 4 categories (the methods of statistical analysis, the way how to describe the statistical techniques, the validity of the used statistical techniques, and the interpretation of the results). RESULTS: With the types of statistics, comparison of mean was most commonly used (51.6%), followed by contingency table (16.1%), regression (15.1%), correlation (9.7%), and etc. (7.5%). With the way of describing the statistical techniques, 28 articles contained full description of every used statistical method, 15 had simply the list of statistical techniques, 2 had some methods omitted in description, and 1 was lack of explanation of statistical method. With the validity of the used statistical techniques, the most powerful statistical method was used in 66.7%, less powerful method in 8.6%, and improper method in 24.7% respectively. With the interpretation of the results, 26 articles drew correct conclusions via proper statistical method, 5 had errors in the interpretation of statistical results, 13 directed to incorrect conclusions due to improper statistical techniques, and 2 could not be judged due to omitted description of statistical method. CONCLUSIONS: We found that univariate or bivariate statistics rather than multivariate statistics were more preferred in JKOS, and authors should be more familiar with broad and precise knowledges of statistics.
Subject(s)
OphthalmologyABSTRACT
PURPOSE: The purpose of this study was to assess the statistical methods used in the Journal of the Korean Society of Emergency Medicine (JKSEM) and to identify the types of errors in statistical analysis. METHODS: We reviewed quantitative articles that were published in the JKSEM from January 1998 through December 2002. Editorials, review articles, and case reports were not included in this analysis. A total of 319 articles was reviewed. We focused on the methods of inferential statistics in these articles. We evaluated the adequacy and the validity of the statistical techniques with our criteria, which were established by modifying Ahn's checklist. RESULTS: Of the 319 articles, 222 used inferential statistics. The t-test was the statistic of choice overall (45.1%), followed by the chi-square test (23.9%). Errors of omission (70.3%) were more frequent than errors of commission. Of the errors of omission, incomplete description of the basic data was the most common. CONCLUSION: We found various mistakes or misuses in the applications of statistical methodologies in the articles published in the JKSEM. The present study suggests that additional efforts should be focused on the appropriateness of the statistical analysis used in JKSEM articles to improve their value, and during the review process, editorial attention should be paid to the validity of the statistical methodologies used in the articles.
Subject(s)
Checklist , Emergencies , Emergency MedicineABSTRACT
BACKGROUND: The Korean Journal of Anesthesiology (KJA) was first published in 1968 containing only 16 articles. In 1998, the number is 291. However, the quantitative growth does not mean a qualitative growth. There are many aspects to improving quality. One of them is statistical accuracy. I have examined the statistical methods in our field and checked the accuracy of the methods. Then, I compared the results with the methods in the 1980s and examined what kinds of changes exist. METHODS: I reviewed all the articles except case reports and review articles in KJA published from 1994 to 1998. I focused on the methods of inferential statistics because those kinds of statistics were usually mentioned in the articles. It is based on the mentioned technique in the article to decide which inferential statistics are used, even though sometimes they are not accurate. I adopted the similar statistical error criteria selected by Ko. RESULTS: Basic statistical error, for example no statistics used even though statistical methods are needed, were dramatically reduced compared to the 1980s. It is increased to use the mean comparison methods correctly, but, some statistical methods are still misused frequently, for example Chi-square test, nonparametric analysis, multiple comparison methods and improperly adopted methods based on the variable scale. CONCLUSION: Generally, based on my criteria statistical errors are reduced from about 75% in the 1980s to about 60% in the 1990s.