Scielo RSS <![CDATA[Bragantia]]> http://www.scielo.br/rss.php?pid=0006-870519420009&lang=pt vol. 2 num. 9 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[<B>Coeficiente de variação e índice de variança</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051942000900001&lng=pt&nrm=iso&tlng=pt The object of the present paper is a study of the usefulness of two relative measures of variation, the well known coefficient oj variation and a new term proposed in this paper and called the index of variance. These terms are defined by the equations : coefficient of variation : σ% = s /v/v. 100 index of variance :σ/ √. 1. It is shown that, for theoretical reasons, only the index of variance may be expected to be constant. Six different experimental series actually proved this constancy, showing at the same time the variability of the coefficient of variation which proved to be dependent upon the respective mean. The coefficient of variation becomes approximately constant when the respective means are sufficiently distant from the absolute limit zero or other biological limits. 2. Thus the index of variance may be used to prove the homogeneity of variation in samples with means of different dimensions. 3. Through this it is shown that the index of variance should be constant, it is explained that for biological reasons we may not always find a good fit between the observed and the expected data, calculated by means of the equation = kv where k represents a biological constant. In two cases a better fit was obtained using more complicated formulae. 4. While it seems justified in agricultural experimentation to accept proportionality between mean yield and area, no such relation exists for the standard error. We may only say that generally the index of variance for large areas is not equal, but bigger than that for smaller ones. 5. The coefficient of variation cannot be used as a general term for comparing the variation in series of different dimensions, where we must apply the index of variance. But it still retains its value as a measure of the efficiency of experiments. <![CDATA[<B>Alguns dados de rendimento de ramí em caule, casca e fibra</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051942000900002&lng=pt&nrm=iso&tlng=pt The object of the present paper is a study of the usefulness of two relative measures of variation, the well known coefficient oj variation and a new term proposed in this paper and called the index of variance. These terms are defined by the equations : coefficient of variation : σ% = s /v/v. 100 index of variance :σ/ √. 1. It is shown that, for theoretical reasons, only the index of variance may be expected to be constant. Six different experimental series actually proved this constancy, showing at the same time the variability of the coefficient of variation which proved to be dependent upon the respective mean. The coefficient of variation becomes approximately constant when the respective means are sufficiently distant from the absolute limit zero or other biological limits. 2. Thus the index of variance may be used to prove the homogeneity of variation in samples with means of different dimensions. 3. Through this it is shown that the index of variance should be constant, it is explained that for biological reasons we may not always find a good fit between the observed and the expected data, calculated by means of the equation = kv where k represents a biological constant. In two cases a better fit was obtained using more complicated formulae. 4. While it seems justified in agricultural experimentation to accept proportionality between mean yield and area, no such relation exists for the standard error. We may only say that generally the index of variance for large areas is not equal, but bigger than that for smaller ones. 5. The coefficient of variation cannot be used as a general term for comparing the variation in series of different dimensions, where we must apply the index of variance. But it still retains its value as a measure of the efficiency of experiments. <![CDATA[<B>Determinação do valor t-s na terra roxa legítima e a aplicação da fórmula Vageler</B>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87051942000900003&lng=pt&nrm=iso&tlng=pt The present work is a study of Vageler's formula y =x.S/ x+y.S for the determination of the final value of the reaction of the cation change in the sorptive complex of the soil. The author took the changeable H+ of the soil as a cation to be examined. Samples studied by the author belong to a chain (a series of soil profiles with 5 horizons each) taken from the original red soil ("terra roxa") of the Ribeirão-Preto Experiment Station. In these samples, as a rule, H+ changed could be considered = T - S, because the Al changed, as far as it existed, was traced in very low percentage, as can be seen in table I. For the determination of T - S, the author used a solution of (CH3COO)2Ca N/l (normal calcium acetate). As a mean of extraction, the percolation of the solution of calcium aceta te through a layer of soil was used instead of the shaking method. From what has been pointed out, it may be concluded that the application of the Vageler formula for the determination of the final value of this reaction is correct and of great advantage. A great amount of material and time is also saved. Besides, the percolation in this kind of work offers a great advantage over the shaking method, consisting of the extraction of changeable ions from the sorptive complex of soil. It has also been observed that the index T - S in this kind of soil is affected by the topography and shows that the more the soil is percolated by water the larger will be the above mentioned index. It has also become evident that organic matter does not contribute in a great extent to the variation of the index T - S.