亲爱的研友该休息了!由于当前在线用户较少,发布求助请尽量完整地填写文献信息,科研通机器人24小时在线,伴您度过漫漫科研夜!身体可是革命的本钱,早点休息,好梦!

Sample Size Calculations in Clinical Research

医学 样本量测定 医学物理学 统计 数学
作者
Peter Bacchetti,Jacqueline M. Leung
出处
期刊:Anesthesiology [Lippincott Williams & Wilkins]
卷期号:97 (4): 1028-1029 被引量:161
标识
DOI:10.1097/00000542-200210000-00050
摘要

To the Editor:—We write to make the case that the practice of providing a priori sample size calculations, recently endorsed in an Anesthesiology editorial, 1is in fact undesirable. Presentation of confidence intervals serves the same purpose, but is superior because it more accurately reflects the actual data, is simpler to present, addresses uncertainty more directly, and encourages more careful interpretation of results. The clinical trial report 2lauded in the editorial in fact serves to illustrate the drawbacks of sample size calculation as a data analysis tool. The a priori calculation presented is based on assumptions about length of stay (normally distributed with a SD of 4.5 days) that did not hold in the actual data, an analysis (comparison of mean length of stay between two groups by t test) that was not presented, and a sample size that was not attained. It therefore does not help the reader interpret the results, which is the proper goal when reporting on a study that has been completed. The post hoc power calculation presented retains most of these deficiencies, and therefore does not help the reader to assess the strength of evidence against a 1.0-day mean advantage for one treatment versus another. In contrast, a confidence interval for the difference in means would directly address this issue. Although the presence of outliers would require a bootstrapping method 3to obtain a valid confidence interval for a difference in means, this bit of extra effort is certainly worthwhile for the central issue of a study, and in any case, much better than relying on convoluted reasoning with invalid power approximations.Perhaps the worst aspect of reporting sample size or power calculations is that it encourages interpretation of studies' results based only on P values, in particular the widespread fallacy of interpreting P > 0.05 as proving the null hypothesis. The other article 4cited by the editorial provides a glaring example of this type of reasoning, concluding that reporting of sample size calculations did not change over time in any journal but did increase overall (see their fig. 2). Returning to the clinical trial report, consider the statement that death rates "were similar" in the four subgroups. While this is an accurate characterization of what was actually observed, unsophisticated readers are liable to interpret this (contrary to the authors' intentions) to mean that the study found strong evidence against any substantial difference in death rates. In fact, the exact 595% confidence interval around the odds ratio for death comparing intravenous versus epidural postoperative analgesia goes from 0.36 to 5.4, which is wide enough to make clear to most readers that this study by itself provides only very weak evidence against a clinically important difference in death rates.We urge reviewers, editors, and quality studies to give authors full credit for providing confidence intervals instead of sample size calculations in reports of completed studies. Indeed, for the reasons illustrated here, it would be best to discourage the practice of using sample size and power calculations as substitutes for more direct assessment of uncertainty using confidence intervals.
最长约 10秒,即可获得该文献文件

科研通智能强力驱动
Strongly Powered by AbleSci AI
更新
PDF的下载单位、IP信息已删除 (2025-6-4)

科研通是完全免费的文献互助平台,具备全网最快的应助速度,最高的求助完成率。 对每一个文献求助,科研通都将尽心尽力,给求助人一个满意的交代。
实时播报
米粒完成签到,获得积分10
刚刚
11秒前
shinian发布了新的文献求助10
17秒前
xiaobo完成签到 ,获得积分10
24秒前
47秒前
赘婿应助科研通管家采纳,获得10
56秒前
56秒前
彩色德天发布了新的文献求助10
1分钟前
量子星尘发布了新的文献求助10
1分钟前
orixero应助老实白云采纳,获得10
1分钟前
呆呆的猕猴桃完成签到 ,获得积分10
1分钟前
1分钟前
tian完成签到,获得积分10
2分钟前
老实白云发布了新的文献求助10
2分钟前
tian发布了新的文献求助30
2分钟前
Yanz完成签到,获得积分10
2分钟前
科研通AI5应助小嘉采纳,获得10
2分钟前
鹿小新完成签到 ,获得积分0
2分钟前
深情安青应助老实白云采纳,获得10
2分钟前
量子星尘发布了新的文献求助10
2分钟前
科研通AI2S应助科研通管家采纳,获得30
2分钟前
科研通AI2S应助科研通管家采纳,获得10
2分钟前
2分钟前
3分钟前
FashionBoy应助黄小渣采纳,获得10
3分钟前
jeff完成签到,获得积分10
3分钟前
3分钟前
小晚完成签到,获得积分10
3分钟前
3分钟前
3分钟前
小嘉发布了新的文献求助10
3分钟前
3分钟前
4分钟前
老实白云发布了新的文献求助10
4分钟前
4分钟前
量子星尘发布了新的文献求助10
4分钟前
Ruri完成签到,获得积分10
4分钟前
4分钟前
清風折柳发布了新的文献求助10
4分钟前
4分钟前
高分求助中
A new approach to the extrapolation of accelerated life test data 1000
Picture Books with Same-sex Parented Families: Unintentional Censorship 700
ACSM’s Guidelines for Exercise Testing and Prescription, 12th edition 500
Nucleophilic substitution in azasydnone-modified dinitroanisoles 500
不知道标题是什么 500
Indomethacinのヒトにおける経皮吸収 400
Phylogenetic study of the order Polydesmida (Myriapoda: Diplopoda) 370
热门求助领域 (近24小时)
化学 材料科学 医学 生物 工程类 有机化学 生物化学 物理 内科学 纳米技术 计算机科学 化学工程 复合材料 遗传学 基因 物理化学 催化作用 冶金 细胞生物学 免疫学
热门帖子
关注 科研通微信公众号,转发送积分 3976649
求助须知:如何正确求助?哪些是违规求助? 3520749
关于积分的说明 11204708
捐赠科研通 3257497
什么是DOI,文献DOI怎么找? 1798716
邀请新用户注册赠送积分活动 877897
科研通“疑难数据库(出版商)”最低求助积分说明 806629