Restrições da correlação nos testes de germinação de sementes e emergência de plântulas / Restrictions of the correlation in the tests of seed germination and seedling emergence

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Coefficient of Pearson r is used to compare scientific tests. In seeds technology it is used to compare results of procedures that measure vigour. When the correspondly similar results are not found in very similar conditions, Persons correlation faces criticism mainly due to two factors. The first one comes from statistics for whose usage of Persons correlation there are prescriptions that are not always observed, when they are not understood as assumption. Variables naturally associated are required with bivariated normal distribution, pairing; homoscedasticity, rectilinear dispersion; detection of outliers. Added to them, there are practical observations in what refers the correlation to be valid only in a restrict range of the data series, the necessity to create value ranges to consider this correlation as good or bad, the need of the graphical analysis, the use and interpretation of the significance, among others. The second cause of odd results would be the existence of several biological factors, which are sometimes support for the reserarcher conclusions. With the objective of identifying applicability of correlations and the causes for odd results of r, there have been compared data existent in the Seeds Analysis Laboratory of ICIAG of the Universidade Federal de Uberlândia-MG, as well as tests of germination of acelerated aging in optimal conditions of repetibility done in laboratory, and tests of field seedling emergency, as well as other simulated variables. The results showed odd results. The normal scattergram between X and Y is enough clear to elucidate only correlated variables of large samples. Although, if the covariance is not as obvious the dispersion Y=f(X) is not enough to show simultaneous increasing or decreasing between variables. With an alternative methodology of plotting the variables related to another auxiliar variable Z of the same n elements of X and Y, we could study the variable behavior in an individual way. It was possible to create graphic criteria to assess non-valid correlations, such as similarity of variables comparable to homoscedastity; influence of outliers on small or big n; grouping of outliers in a dissident range, influence of treatments effect. In the analysed cases, we concluded that, comparing seeds vigour with only laboratory results, as well as its relation with the field results and among simulated data, the results inconsistency of correlations are prevalent as they do not follow the literature prescriptions, among others. The magnitude of the distortions due to statistical causes did not leave space for measuring effects of the variation of the biological seeds conditions, temporal alterations related to management or the edafoclimatic ones. Keywords: 1. Failure in correlations 2. Correlation reliability

ASSUNTO(S)

confiabilidade de correlações detectar outliers na correlação sementes prescriptions of correlation use prescrições da correlação falhas em correlações homoscedasticidade nas correlações agronomia estatística agrícola germinação failure in correlations correlation reliability homoscedasticity in correlations outliers detection in the correlation

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