Schätzung von Standardfehlern und Kausaleffekten in der empirischen Wirtschaftsforschung – Methoden und Anwendungen

This paper discusses methodological problems of standard errors and treatment effects. First, heteroskedasticity- and cluster-robust estimates are considered as well as problems with Bernoulli distributed regressors, outliers and partially identified parameters. Second, procedures to determine treatment effects are analyzed. Four principles are in the focus: difference-in-differences estimators, matching procedures, treatment effects in quantile regression analysis and regression discontinuity approaches. These methods are applied to Cobb-Douglas functions using IAB establishment panel data. Different heteroskedasticity-consistent procedures lead to similar results of standard errors. Cluster-robust estimates show evident deviates. Dummies with a mean near 0.5 have a smaller variance of the coefficient estimates than others. Not all outliers have a strong influence on significance. New methods to handle the problem of partially identified parameters lead to more efficient estimates. The four discussed treatment procedures are applied to the question whether company-level pacts affect the output. In contrast to unconditional difference-in-differences and to estimates without matching the company-level effect is positive but insignificant if conditional difference-in-differences, nearest-neighbor or Mahalanobis metric matching is applied. The latter result has to be specified under quantile treatment effects analysis. The higher the quantile the higher is the positive company-level pact effect and there is a tendency from insignificant to significant effects. A sharp regression discontinuity analysis shows a structural break at a probability of 0.5 that a company-level pact exists. No specific effect of the Great Recession can be detected. Fuzzy regression discontinuity estimates reveal that the company-level pact effect is significantly lower in East than in West Germany

Determinação da carga de treino nos exercícios supino e rosca bíceps em mulheres jovens Defining the training load in bench press and biceps curl exercises in young women

O objetivo deste estudo foi avaliar a força máxima dinâmica (1RM) nos exercícios supino e rosca scott, e relacioná-la com a massa corporal total (MCT) e com a massa corporal magra (MCM), bem como avaliar o número máximo de repetições em diferentes percentuais de 1RM. Onze mulheres (24 ± 1,4 anos) foram submetidas à avaliação da composição corporal, testes de 1RM e testes de repetições máximas em 50, 60, 70 e 80% de 1RM. No tratamento dos dados, foram utilizados a regressão linear múltipla, a ANOVA para medidas repetidas e o teste t pareado. A MCM é a variável que melhor explica a variância de 1RM, podendo ser utilizada para a determinação de um coeficiente para a estimativa da carga de treino. Houve diferenças significativas entre os números de repetições em todos os percentuais e em ambos os exercícios [(supino (p=0,000) e rosca scott (p=0,000)], sendo esses números progressivamente menores com o incremento da carga.<br>The purpose of this study was to assess maximum strength (1RM) in the bench press and biceps curl exercises, and relate it to total body mass (BM) and fat-free mass (FFM), as well as to assess the maximum repetition number at different percentages of 1-RM. Eleven women (age: 24 ± 1.4 years) were submitted to body composition assessment, 1-RM tests, and maximum repetition tests at 50, 60, 70 and 80% of 1-RM. For data treatment, multiple linear regression, repeated measures ANOVA and paired t-test were used. FFM explains better than BM the 1-RM variance and can be used to determine a coefficient to estimate the training load. Significant differences were found in the maximum repetition numbers in all percentages and both exercises (bench press (p=0,000) and biceps curl (p=0,000). These results revealed a gradual decrease in the number of repetitions as the load increased

Characterization of the LIGO detectors during their sixth science run

In 2009-2010, the Laser Interferometer Gravitational-Wave Observatory (LIGO) operated together with international partners Virgo and GEO600 as a network to search for gravitational waves (GWs) of astrophysical origin. The sensitivity of these detectors was limited by a combination of noise sources inherent to the instrumental design and its environment, often localized in time or frequency, that couple into the GW readout. Here we review the performance of the LIGO instruments during this epoch, the work done to characterize the detectors and their data, and the effect that transient and continuous noise artefacts have on the sensitivity of LIGO to a variety of astrophysical sources