Efecto de edad relativa en la Liga Nacional de Básquetbol de Chile (LNB) / Relative Age Effect in Chile's National Basketball League (LNB)

RESUMEN: El objetivo del estudio fue verificar la existencia de sobrerrepresentación de jugadores nacidos en la primera parte del año o Efecto de Edad Relativa (EER), en la elite del baloncesto masculino chileno.A partir de las nóminas oficiales de la Liga Nacional de Básquetbol de Chile (LNB) para la temporada 2019-20, se obtuvieron las distribuciones por mes, trimestre y semestre, de las fechas de nacimiento de los jugadores. Estas fueron comparadas con las distribuciones de nacimientos en Chile entre 1977 y 2005. La significancia estadística de las diferencias entre distribuciones esperadas y observadas se verificó mediante la prueba de χ2 (mensual y trimestral) y una distribución binomial (semestral).Los tres análisis arrojaron diferencias significativas entre las distribuciones esperadas y observadas, con una sobrerrepresentación de los nacidos en el primer semestre, primer trimestre y el mes de enero y subrepresentación de los nacidos el segundo semestre, cuarto trimestre y mes de diciembre. Se concluye que hay evidencia suficiente para confirmar la existencia de EER en LNB.Para disminuir el EER se proponen medidas tendientes a educar a entrenadores acerca de los efectos de las diferencias de edad en el rendimiento y el establecimiento de fechas de corte móviles durante la temporada competitiva.

ABSTRACT: The objective of the study was to verify the existence of overrepresentation of players born in the first part of the year or Relative Age Effect (RAE), in Chilean elite men's basketball.The distribution by month, quarter, and semester of players' birthdates were obtained from the official rosters of the National Basketball League of Chile (LNB) for the 2019-20 season. These were compared to the distribution of births in Chile between 1977 and 2005. The statistical significance of the differences between expected and observed distribution was verified using the 2 test (monthly and quarterly) and a binomial distribution (semi-annual).The three analyses yielded significant differences between the expected and observed distribution, with an overrepresentation of those born in the first semester, first quarter, and January and an underrepresentation of those born in the second semester, fourth quarter, and December. It is concluded that there is sufficient evidence to confirm the existence of RAE in LNB.To reduce RAE, measures are proposed to educate coaches about the effects of age differences on performance and the establishment of mobile cut-off dates during the competitive season.

A natural robustification of the ordinary instrumental variables estimator.

Instrumental variables estimators are designed to provide consistent parameter estimates for linear regression models when some covariates are correlated with the error term. We propose a new robust instrumental variables estimator (RIV) which is a natural robustification of the ordinary instrumental variables estimator (OIV). Specifically, we construct RIV using a robust multivariate location and scatter S-estimator to robustify the solution of the estimating equations that define OIV. RIV is computationally inexpensive and readily available for applications through the R-library riv. It has attractive robustness and asymptotic properties, including high resilience to outliers, bounded influence function, consistency under weak distributional assumptions, asymptotic normality under mild regularity conditions, and equivariance. We further endow RIV with an iterative algorithm which allows for the estimation of models with endogenous continuous covariates and exogenous dummy covariates. We study the performance of RIV when the data contains outliers using an extensive Monte Carlo simulation study and by applying it to a limited-access dataset from the Framingham Heart Study-Cohort to estimate the effect of long-term systolic blood pressure on left atrial size.

Linfoma No-Hodgkin del tracto gastrointestinal / Lynfoma non Hodgkin in gastrointestinal tract

Se presenta el caso de un paciente joven con una masa abdominal, diagnosticado a través de biopsias tomadas durante colonoscopía. El diagnóstico patológico correspondió a Linfoma No-Hodgkin. Difuso de célulasGrandes Tipo B. El tratamiento consistió en combinación de quimioterapia, demostrándose respuesta completa de tipo endoscópico, radiológico y patológico