OBJECTIVE To determine the relationship between anthropometric indices and the age of menarche in female students of Sabzevar, Iran. METHODS The cross-sectional study was conducted in Sabzevar, Iran, from April to September 2010, and involved girls of 11-18 years of age. The required sample size for analysing the relationship between menarche age and Body Mass Index was estimated to be 110 by...

In the design of a randomized clinical trial with one pre and multiple post randomized assessments of the outcome variable, one needs to account for the repeated measures in determining the appropriate sample size. Unfortunately, one seldom has a good estimate of the variance of the outcome measure, let alone the correlations among the measurements over time. We show how sample sizes can be cal...

Due to the small number of replicates in typical gene microarray experiments, the performance of statistical inference is often unsatisfactory without some form of information-sharing across genes. In this article, we propose an enhanced quantile rank score test (EQRS) for detecting differential expression in GeneChip studies by analyzing the quantiles of gene intensity distributions through pr...

Effective management of wetland quantity and quality is crucial for effective conservation of declining amphibian populations. In particular, frogs and toads that employ aggregative breeding strategies may suffer negative population impacts in response to changes in availability of aquatic breeding habitat, including overabundance of suitable habitat, if density of conspecifics attending aggreg...

BACKGROUND Bleeding time test is used to assess the function of platelets in human body. The aim of this project was thus to estimate the sample size required to determine the normal range of bleeding time (BT) in Borujerd (a city in Iran). A pilot study was designed to determine the range of normal BT in a small group of normal people. The total sample size for the next study was then calculat...

REPLY Sir, It is a matter of satisfaction that our article has generated interest. We would like to respond to each of the observations by Agarwal (2000) one by one. (1) We are in complete agreement with the author of this ' letter to editor' that the usage of term non-parametric and parametric variables is not technically sound. However, the conventional usage of these terms is seen in many sc...

This study sought to determine the guidance and counselling services which Social Science students in one Government-owned university in Zimbabwe had received in high school and the guidance and counselling services that they desired upon entry into university. Variations in services received in high school and those desired at university were by school type of the respondents. More specificall...

BACKGROUND The removal of outliers to acquire a significant result is a questionable research practice that appears to be commonly used in psychology. In this study, we investigated whether the removal of outliers in psychology papers is related to weaker evidence (against the null hypothesis of no effect), a higher prevalence of reporting errors, and smaller sample sizes in these papers compar...

Researchers occasionally have to work with an extremely small sample size, defined herein as N ≤ 5. Some methodologists have cautioned against using the t-test when the sample size is extremely small, whereas others have suggested that using the t-test is feasible in such a case. The present simulation study estimated the Type I error rate and statistical power of the oneand two-sample ttests f...