coincides with the standard (central) tν distribution. In the following, represents the effect size; by convention, a of 0.5 is considered a "medium" effect size. In Figure 1 are shown three instances of the t′ density envelope for ν = 10, one with δ = 0 (a standard t), and two with δ = 3 and δ = 6 : one may note that, whereas t10(δ = 0) is centered at 0 and symmetrical, the non-central t′’s ar...

Many Six Sigma practitioners use “Student’s” independent two-sample t-test when investigating differences in means. This type of test is based upon drawing random samples from two independent normal (Gaussian) distributions. Often, however, the assumption of normality and/or random sampling is violated. This article discusses when and why the two-sample t-test may be considered robust to these ...

Five inferential methods employed in single-case studies to compare a case to controls are examined; all of these make use of a t-distribution. It is shown that three of these ostensibly different methods are in fact strictly equivalent and are not fit for purpose; they are associated with grossly inflated Type I errors (these exceed even the error rate obtained when a case's score is converted...

In clinical research, comparisons of the results from experimental and control groups are often encountered. The two-sample t-test (also called independent samples t-test) and the paired t-test are probably the most widely used tests in statistics for the comparison of mean values between two samples. However, confusion exists with regard to the use of the two test methods, resulting in their i...

several studies have shown that decidual tissue produces soluble factors which can mediate a variety of immunosuppressive activities. in order to assess whether prostaglandin e2 (pge2) was present in supernatants produced by explant culture of 10 human specimens of first trimester decidua. the effect of the supernatants from the two different series (with and without indomethacin treatment) of ...

liquid-phases adsorption equilibrium of phenol onto two naturally available soils namely kalathur soil (kr) and adhanur soil (ar) were studied. the experimental data were analyzed using fourteen isotherm models, ranging from single-parametric model to multi-parametric models (up to 5 parameters) of the system. results show that in general the accuracy of models to fit experimental data improve...

This research assessed the effectiveness of interdisciplinary interventions involving physicians, pharmacists and nutritionists, aimed at the promotion of the Rational Use of Drugs. It is a study of a prospective and analytical nature conducted with a population of elderly females, where the effectiveness of the intervention was assessed according to indicators of the Rational Use of Drugs esta...

It is shown that the global power function of any nonparametric test is at on balls of alternatives except for alternatives coming from a nite dimensional sub-space. The present benchmark is here the upper one-sided (or two-sided) envelope power function. It turns out that also the level points are far away from the corresponding Neyman Pearson test level points except for a nite number of orth...