BACKGROUND Central to the design of a randomised controlled trial is the calculation of the number of participants needed. This is typically achieved by specifying a target difference and calculating the corresponding sample size, which provides reassurance that the trial will have the required statistical power (at the planned statistical significance level) to identify whether a difference of...

A sample size calculation for logistic regression involves complicated formulae. This paper suggests use of sample size formulae for comparing means or for comparing proportions in order to calculate the required sample size for a simple logistic regression model. One can then adjust the required sample size for a multiple logistic regression model by a variance inflation factor. This method re...

Exact power and sample size calculation for bioequivalence studies with high order crossover designs using statistical software nQuery are presented. Such calculation can be very easily performed, and thus provides a convenient tool for practical usage.

In clinical research, parameters required for sample size calculation are usually unknown. A typical approach is to use estimates from some pilot studies as the true parameters in the calculation. This approach, however, does not take into consideration sampling error. Thus, the resulting sample size could be misleading if the sampling error is substantial. As an alternative, we suggest a Bayes...

راش، گونه­های علفی، حاصل خیزی خاک، آنالیزهای چندمتغیره. this study was carried out in carpino-fagetum orientalis, rusco-fagetum orientalis,fagetum oriental and alno-fagetum orientalisforest communities of namkhaneh, gorazbon and chelir districts of kheiroudkenar forest. the aim of the research was investigation on relationship between understory vegetation and soil condition and to determine th...

silvicultural operation need to notice the species diversity. to this study gomarlang district in marivan region, northern zagros forest was selected. in this study 30 circle sample plots (500 m2) were collected by random method. in every sample plot the kind of species and number of trees and shrub were recorded. in the sample plots the micro plots of 5 m by 5 m (i.e. area of 25 m2) were desig...

INTRODUCTION Transbronchial lung cryobiopsy (TBLC) is increasingly used in the diagnosis of diffuse lung disease (DLD), but no data have yet been published on the learning curve associated with this technique. AIM To evaluate diagnostic yield, lung tissue sample length and area, and procedure-related complications in a cohort of TBLC procedures to define the learning curve and threshold for p...

In this research, the metal-organic framework of HKUST-1 (Hong Koung University of Science and Technology) was synthesized for use in modern drug delivery systems by the thermal solvent method. It was activated in two conditions: under vacuum pressure and by a freeze-drying method. The synthesized HKUST-1 Metal-Organic Framework was analyzed by IR, XRD, BET, and SEM. In order to examine and com...

different ecologic factors influence on forming, development and sustaining of the plant communities, among which physiographic variables are the most important ones. the aim of this study was to identify forest types and effect of physiographical factors such as sea level height, slope and aspect of the site on quantitative characteristics of forest types in 2nd district of vaz forest with are...