Anthropometric profile and conditional factors of U21 Spanish elite beach volleyball players according to playing position (Perfil antropométrico y factores condicionales de los jugadores españoles élite sub-21 según la posición de juego)

The aim of this work was to describe and study the relationship between anthropometric and conditional factors of under-21 high-performance beach volleyball players according to playing position. The sample consisted of 5 male teams (5 blockers and 5 defenders) belonging to Spanish men’s national beach volleyball team or participants in international tournaments. Anthropometric profile was assessed following the guidelines proposed by ISAK. The tests performed to assess conditional factors were: vertical jump (SJ, CMJ and ABK), 5- and 10-m sprint (S5m and S10m), agility test (AT) and overhead medicine ball throw in a standing position (OTSP) and on knees position (OTKP). Mann-Whitney U test was applied to compare blockers and defenders and Pearson correlation coefficient (r) was used to determine the relationships between anthropometric and conditional variables. The results showed that U21 Spanish beach volleyball players had lower values for height and body weight than international players of the same category. Regarding playing position, blockers showed higher values of height, weight, muscle mass and bone weight than defenders (p<0.05). The somatotype for blockers and defenders were classified as ecto-mesomorph. Relationships have been found between anthropometric variables (height, weight, bone, muscle and fat) and conditional factors. The conditional tests did not show significant differences between blockers and defenders except those which required to mobilize an external weight, in which case blockers showed a better performance. Resumen. El objetivo del presente trabajo fue describir y estudiar la relación existente entre el perfil antropométrico y los factores condicionales de los jugadores de voleibol de playa de alto rendimiento en la categoría sub-21 en función de la posición de juego. La muestra consistió en 5 equipos (5 bloqueadores y 5 defensores) pertenecientes al equipo nacional de voleibol de playa masculino o participantes en torneos internacionales. El perfil antropométrico se evaluó siguiendo las pautas propuestas por ISAK. Las pruebas realizadas para evaluar los factores condicionales fueron: salto vertical (SJ, CMJ y ABK), sprint de 5 y 10 m (S5m y S10m), prueba de agilidad (AT) y lanzamiento de balón medicinal de pie (OTSP) y en posición de rodillas (OTKP). La prueba U de Mann-Whitney se aplicó para comparar los datos obtenidos de los bloqueadores y defensores, mientras que el coeficiente de correlación de Pearson (r) se utilizó para determinar las relaciones entre las variables antropométricas y el rendimiento del juego. Los jugadores españoles sub-21 mostraron valores más bajos en variables como el peso y la altura cuando fueron comparados con jugadores internacionales de la misma categoría. Los bloqueadores presentaron valores más elevados en cuanto a la altura, peso, masa muscular y peso óseo que los defensores (p<0,05). El somatotipo tanto para los bloqueadores como para los defensores se clasificó como ecto-mesomorfo. Se encontraron relaciones entre las características antropométricas (altura, el peso, masa ósea, masa muscular y componente graso) y los factores condicionales. Las pruebas de rendimiento no mostraron diferencias significativas entre posiciones de juego, excepto en aquellas en las que se tuvo que movilizar una carga externa, en cuyo caso los bloqueadores mostraron mejores resultados.

On powerful exact nonrandomized tests for the Poisson two-sample setting

In the case of two independent samples from Poisson distributions, the natural target parameter for hypothesis testing is the ratio of the two population means. The conditional tests which have been derived for this class of problems already in the 1940s are well known to be optimal in terms of power only when randomized decisions between hypotheses are admitted at the boundary of the respective rejection regions. The major objective of this contribution is to show how the approach used by Boschloo in 1970 for constructing a powerful nonrandomized version of Fisher’s exact test for hypotheses about the odds ratio between two binomial parameters can successfully be adapted for the Poisson case. The resulting procedure, which we propose to term Poisson-Boschloo test, depends on some cutoff for the observed total number of events, the variable upon which conditioning has to be done. We show that for any fixed specific alternative, this cutoff can be chosen in such a way that the resulting nonrandomized test falls short in power of the randomized UMPU test only by a negligible amount. Thus, sample size calculation for the Poisson-Boschloo test can be carried out nearly exactly by means of the same computational procedure as has to be used for the randomized UMPU test. Since the power of the latter is accessible to elementary computational tools, this result makes approximate methods of sample size calculation for the Poisson-Boschloo test dispensable. It is furthermore shown how the construction of a Poisson-Boschloo type test extends to the case that interest is in establishing equivalence in the strict, two-sided sense rather than noninferiority. Although proceeding to two-sided equivalence considerably complicates the construction, comparing the resulting test procedure in terms of power with the exact randomized UMPU test leads essentially to the same conclusions as in the noninferiority case.

Randomization Tests that Condition on Non-Categorical Covariate Balance

A benefit of randomized experiments is that covariate distributions of treatment and control groups are balanced on average, resulting in simple unbiased estimators for treatment effects. However, it is possible that a particular randomization yields covariate imbalances that researchers want to address in the analysis stage through adjustment or other methods. Here we present a randomization test that conditions on covariate balance by only considering treatment assignments that are similar to the observed one in terms of covariate balance. Previous conditional randomization tests have only allowed for categorical covariates, while our randomization test allows for any type of covariate. Through extensive simulation studies, we find that our conditional randomization test is more powerful than unconditional randomization tests and other conditional tests. Furthermore, we find that our conditional randomization test is valid (1) unconditionally across levels of covariate balance, and (2) conditional on particular levels of covariate balance. Meanwhile, unconditional randomization tests are valid for (1) but not (2). Finally, we find that our conditional randomization test is similar to a randomization test that uses a model-adjusted test statistic.

The Pure Expectations Theory and Quarterly Interest Rate Premiums

The expectations theory posits that the long interest rate is an average of expected short term interest rates with the possibility of the existence of a risk premium. This paper looks upon fourteen samples of investments for which the difference in maturity is three months. All yields are actual yields and are adjusted to have the same maturities as the short rate. The evidence is strong for the pure expectations theory which predicts that the risk premiums are zero. This should not be surprising because the premium that we are looking for is merely 4 basis points per quarter. The contribution of this paper, besides giving support to the pure expectations theory, is to lay out the fundamental and basic methodology that one should follow in order to study other investments similar to ours. Both unconditional and conditional tests are performed. Because of sampling error and small-sample bias the unconditional tests may be preferable.