vol. 1 núm. 1 (2008)

The purpose of this paper is to communicate some recent results about survival analysis under the Kaplan-Meier curve and its aplication to censored data by resampling methods such as Jackknife y Boostrap.

In the basic texts, the definition of the expected value of a random variable is different from the definition given in a probability course based on the theory of measure. In this manuscript it is shown why both definitions are in fact equivalent.

The aim of this paper is to divulge the modification of the Pen˜a y Rodr´ıguez test (2002) of goodness of fit. This test is asymptotically equivalent, but it is more powerful than the previous one. Two approaches are proposed using the gamma and the normal distributions. By an empirical example it is shown that theproposedtest ismore powerfulthanLjung-Boxtestand Montitestof nonlinear models detection.

I evaluated the difference of the tenderness between bovine meats in different ages within the normal ranks to which these animals are taken to sacrifice, being calculated its indices of greasy deposition according to sex due to the differences of this characteristic found between males and females, similarly with bullfighting and indicus races. In order to determine the fat concentration in each one of the samples and evaluation of tenderness a Warner Bratzler texturometer was used. The collected data were analyzed through a multiple linear regression model. The analysis of the results indicates that in the bovine cattle, the differences of terneza by increase of fat deposition are also are carried out to superior ages, although the relation is inverse. The percentage of fat including within each muscular piece is directly related to greater tenderness. Minors sacrifice ages produce minors resistance to the cut.

Statistics is the most widely applied of all mathematical disciplines and at the center of statistics lies the normal distribution, known to millions of people as the bell curve, or the bell-shaped curve. In this paper, the evolution of the most important probability distribution during several centuries is presented.

The Statistics Faculty in the Universidad Santo Tom´as de Colombia has just issued its new semestral publication named Comunicaciones en Estad´ıstica. This is the first paper of the journal in which the editorial committee attempts to unify the presentation of the papers that are submitted. It is recalled that this is just a guide that authors could considered but it is clear that variations of the presentation are allowed.

Con orgullo nos complace presentar ante la comunidad académica nacional e internacional (compuesta por docentes, decanos de facultades y departamentos, estudiantes, egresados, integrantes y directores de grupos de investigación), ante el sector público gubernamental, como principal usuario de las estadísticas oficiales (con instituciones de planeación estratégica nacional, políticas públicas, institutos nacionales de estadística, bancos centrales, ministerios de desarrollo, entre otros), y ante el sector privado empresarial en cada uno de sus frentes, como impulsador y beneficiario de las técnicas estadísticas, esta publicación seriada semestral llamada Comunicaciones en Estadística.