background and aim: academic achievement, especially in hard-of-hearing students, is hinged on their writing skills, and writing skill deficiency can adversely affect their cross-disciplinary skills. the purpose of this study was to explore and delineate the writing skill curriculum for hearing-impaired students in primary school system of iran and to develop an exploratory model. methods: in t...

Background: The calculation of the sample size is one of the most important steps in designing a randomized controlled trial. The purpose of this study is drawing the attention of researchers to the importance of calculating and reporting the sample size in randomized controlled trials.    Methods: We reviewed related literature and guidelines and discussed some important issues in s...

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Sample size estimation is an essential step in the design of clinical trials. For normal data, the calculation is based on estimates of the mean and variance of the treatment effect. These estimates are often unreliable because they are based on smaller studies, possibly looking at a different population than the one of interest. If the true treatment effect is overestimated and/or the variance...