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Báo cáo y học: " tatistics review 3: Hypothesis testing and P values."

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học General Psychiatry cung cấp cho các bạn kiến thức về ngành y đề tài: tatistics review 3: Hypothesis testing and P values. | Critical Care June Vol 6 No 3 Whitley and Ball Review Statistics review 3 Hypothesis testing and P values Elise Whitley1 and Jonathan Ball2 1 Lecturer in Medical Statistics University of Bristol Bristol UK 2Lecturer in Intensive Care Medicine St George s Hospital Medical School London UK Correspondence Editorial Office Critical Care editorial@ccforum.com Published online 18 March 2002 Critical Care 2002 6 222-225 2002 BioMed Central Ltd Print ISSN 1364-8535 Online ISSN 1466-609X Abstract The present review introduces the general philosophy behind hypothesis significance testing and calculation of P values. Guidelines for the interpretation of P values are also provided in the context of a published example along with some of the common pitfalls. Examples of specific statistical tests will be covered in future reviews. Keywords hypothesis testing null hypothesis P value The previous review in this series described how to use confidence intervals to draw inferences about a population from a representative sample. A common next step in data analysis is calculation of P values also known as hypothesis testing. Hypothesis testing is generally used when some comparison is to be made. This comparison may be a single observed value versus some hypothesized quantity e.g. the number of babies born in a single delivery to mothers undergoing fertility treatment as compared with typical singleton birth or it may be a comparison of two or more groups e.g. mortality rates in intensive care unit patients who require renal replacement therapy versus those who do not . The choice of which statistical test to use depends on the format of the data and the study design. Examples of some of the more common techniques will be covered in subsequent reviews. However the philosophy behind these statistical tests and the interpretation of the resulting P values are always the same and it is these ideas that are covered in the present review. The null hypothesis A typical research question is