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1、Chapter 13 Design of medical researchChapter 13 Design of Medical Research(I)design 设计设计 research design 研究设计研究设计 reliable 可靠可靠 random error 随机误差随机误差 efficiency 效率效率 laboratory experiment 实验室实验实验室实验 clinical trial 临床试验临床试验 medical survey 医学调查医学调查 control 对照、对照组对照、对照组 balance 均衡均衡 randomization 随机化随机
2、化 replication 重复重复 treatment 处理处理 subject 对象对象 effect 效应效应 empty control 空白对照空白对照 placebo 安慰剂安慰剂 mutual control 互相对照互相对照 self control 自身对照自身对照 standard control 标准对照标准对照 historical control 历史对照历史对照 homogeneity 均匀性均匀性 homogeneous 均匀的均匀的 prerequisite 前提条件前提条件 casual 随意随意 reproduce 重复重复 pilot study 预试验预
3、试验 blood sedimentation 血沉血沉 chemotherapy 化学疗法化学疗法 remission rate 缓解率缓解率 subject selection 对象选择对象选择 treatment assignment 处理安排处理安排 data collection 数据搜集数据搜集 validity 效度效度 reproducible 可重复可重复 animal experiment 动物实验动物实验 community intervention trial 社区干预试验社区干预试验 intervene 干预干预 eligible subjects 合格对象合格对象 f
4、actor 因素因素 treatment factor 处理因素处理因素 non-treatment factors 非处理因素非处理因素 level 水平水平 objective 客观性客观性 accurate 准确准确 precise 精确精确 specific 特异的特异的 sensitive 敏感的敏感的 The aim of research design:l To get a reliable result in the lowest cost of manpower,time and money;l To estimate the random error within the
5、observed data;l To promote the efficiency of the research There are two kinds of research:l Laboratory experiment and Clinical triall Medical survey1.Control 2.Balance 3.Randomization 4.Replication 1.ControllIf there is no control,then there is no comparison.OthersEffect of othersEffect of treatment
6、TreatmentSubjectOthersControlEffect of controlSubjectEffect of otherslSome forms of control:(1)Empty control(2)Placebo control (for animal,Experimental control)(3)Mutual control(4)Self control(5)Standard control(6)Historical controlOthersEffect of othersEffect of treatmentTreatmentSubject AOthersSub
7、ject BEffect of othersOthersEffect of othersEffect of treatmentTreatmentSubject AOthers PlaceboEffect of placeboSubject BEffect of othersOthersEffect of othersEffect of Treatment A Treatment I Subject AOthersTreatment II Effect ofTreatment B Subject BEffect of othersOthersEffect of othersEffect of t
8、reatmentTreatmentSubjectOthersControlEffect of controlSubjectEffect of othersOthersEffect of othersEffect of treatmentTreatmentSubjectThere is no control group,but compare with certain“standard”There is no control group,but compare with“historical result”OthersEffect of othersEffect of treatmentTrea
9、tmentSubject 2.Balance:The experimental group and control group are almost the same in all aspects except the treatment.OthersEffect of othersEffect of treatmentTreatmentSubjectOthersControlEffect of controlSubjectEffect of others 3.Randomization Many factors,we know that they may influence the resu
10、lts,but they are very difficult to deal with Randomization is the best choice!Example To improve the homogeneity of subjects,collect a number of students with same age and gender;randomly arrange them into two groups to make them balance in height and weight.lRandomization is the prerequisite of sta
11、tistical inference.lRandomization CasuallRandomization means that all subjects in population have same probability to be sampled out for research.4.ReplicationlOne meaning of replication:The results can be reproduced in different labs and by different researchers.lAnother meaning of replication:The
12、study should be performed in a big enough sample.Altman&Dore checked 90 papers:l39%mentioned their sample size and why.lSample sizes of 27%papers were too small to make a conclusion.How to estimate sample size in the design stage?Four parameters are needed:(1):the maximal probability of type error i
13、s allowed(2):the maximal probability of type I error is allowed(3):the minimal difference between two means is allowed(4):the standard deviation among subjects in the same group Check Table 13-2,or calculate byExample 13-1 A pilot study shows,the sample mean andstandard deviation of pulse among male
14、 patients with leadpoisoning are 67/min and 5.97/min respectively.To testwhether the population mean of this kind of patients islower than the mean of normal males(one-side test),howmany cases are needed?Given ,take (Check Table 13-2,/0.85,n=14)1.Comparison between the mean and a given number2)(uun1
15、0.0,05.097.5,567721321.12597.5)282.1645.1()(22uun)or ,or(:,:000100HHCheck Table 13-2,or calculate byExample 13-2 Comparing mean reductions of blood sedimentationbetween drug A and B.To test whether the effects of two drugs aredifferent(two-side),how many cases are needed?A pilot study shows,.Take ,.
16、(Check Table 13-3,/0.60,n=60)2.Comparison between two means of two independent samples211210:,:HH221)(2uunnmm/h98.2 mm/h,0.5 mm/h;93.1 mm/h,2.32211SXSX98.2,8.12.30.510.0,05.0586.578.198.2)282.196.1(2)(22221uunn3.Comparison between two frequencies of twoindependent samples 211210:,:HHCheck Table 13-4,or calculate byExample 13-3 Comparing two chemotherapies for lymphoma,how many cases are needed?The pilot study shows,the remission rates are .Given .(Check Table 13-4,n=35)221)(2uunn2,)1(,2121pppppp
