BACKGROUND During the last 30 years, the median sample size of research studies published in high-impact medical journals has increased manyfold, while the use of non-parametric tests has increased at the expense of t-tests. This paper explores this paradoxical practice and illustrates its consequences. METHODS A simulation study is used to compare the rejection rates of the Wilcoxon-Mann-Whi...

BACKGROUND The present investigation compared parenting practices in a sample of preschoolers whose mothers reported smoking during pregnancy versus those who did not. METHODS A sample of n = 216, 3.0- to 5.11-year-old children, participants in an ongoing longitudinal study, was separated into those reportedly exposed to smoking in utero and those who were not. Parenting practices were compar...

The behaviour of group sequential tests in the two-sample problem is investigated if one replaces the classical non-robust estimators in the t-test statistic by modern robust estimators of location and scale. Hampel's 3-part redescending M-estimator 25A used in the Princeton study and the robust scale estimators length of the shortest half proposed by Rousseeuw & Leroy and Q proposed by Roussee...

Ask experts what would be an important reduction in amount consumed. Need some idea of the SD of a within-child difference in consumption from a four hour period in one day to a four hour period in another day. Could do a pilot study with say 10 children measured [without any intervention] on two different days and get the SD of the 10 differences. Then use sample size formula for 1 sample t-te...

several studies and researches have been conducted in the world since 1950 to assess and evaluate the media news credibility, and in this regard the researches tried to investigate the media news from different angles. the finding of any such researches and studies quite indicate that the credibility is a multidimensional construct and thus, a reliable and successful survey in this connection i...

although extensive experimental work has been carried out during the last several years, experimental reaction rate constants are available only for hundreds of compounds. therefore, it is useful to develop a theoretical prediction method, which can be used to obtain estimates of the necessary kinetic parameters. one of the most successful approaches to predict chemical properties starting only...

background: mental disorders have an important relationship with work conditions. excessive workload, laborers needs and expectations ignorance, harmful physical agents, noise, poor lightning and bad work atmosphere result increasing stress and job dissatisfaction in workers . methods: this descriptive-analytical survey implemented in order to investigate stress and job satisfaction rate of one...