一项研究需要进行多少次?观察多少个病例才能获得足以下结论的数据?这是临床研究中非常现实而为具体工作者所关心的问题。一般地说,病例数多,样本大些,对总体情况的反映能全面些,研究的结果与结论也与实际情况接近些;观察的例数不足,样本太小,难免带有一 How many times does a study need to be conducted? How many cases can be observed to obtain sufficient data for conclusions? This is a very real issue in clinical research and a concern for specific workers. Generally speaking, the number of cases is large and the sample is larger. The overall situation can be reflected more comprehensively. The results and conclusions of the research are also close to the actual situation. The number of observations is insufficient, the sample is too small, and it is inevitable to have a