1、,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,20046,*,为何要做统计分析?,统计分析目标是应用,样本,资料信息,作出相关,研究总体,有效推测。,应用,概要性指标,描述样本资料来实现。,这些概要性指标保留了,足够信息,去预计研究总体特征。,6,1,第1页,关于总体临床研究问题,在发展中国家,人工喂养相比母乳喂养能否增加母亲为HIV阳性婴儿生存率?,怎样建立一个心脏搭桥手术后生存率模型?病人特征能否预测术后生存率?相比内科治疗,搭桥手术后1,3,5年生存率能否改进?,局部治疗小肝癌能否代替外科手术切除?,根治术后应用大剂量干扰素能否降低肝癌复发率?,6
2、,2,第2页,今天主题,总体,样本和个体,资料类型:Continuous vs.categorical,怎样描述资料?统计量 和图,测量集中趋势和离散趋势,标准误和95%可信区间,依据数据选择适当统计方法,诊疗试验评价,6,3,第3页,总体,样本和个体,“Aristotle maintained that women have fewer teeth than men;although he was twice married,it never occurred to him to verify this statement by examining his wives mouths.”-Si
3、r Bertrand Russell,The Impact of Science on Society,1952.,“It is a capital mistake to theorize before you have data.”-Sir Arthur Conan Doyle,Scandal in Bohemia,.,6,4,第4页,总体,样本和个体,And,for another viewpoint:,“If your experiment needs statistics,you ought to have done a better experiment.”Ernest Ruther
4、ford.,The bench science perspective:you can control all the variables!Clinicians,however,know better human variation is large,and often inexplicable.Statistics help us describe it and generalize at least enough to improve our ability to practice medicine.,6,5,第5页,总体,样本和个体,Aristotle 推测了一个,女性总体,(比较男性总
5、体).他实际上手头就有一个包含,2个女人样本,,他能对这个样本中2个,个体,进行数牙。,The,population,is the collection of all people about whom you would like to ask a research question.This might be a fairly clear-cut easily defined set of people:,“What proportion of people 65 or older in the US today have Alzheimers disease?”,Or it might
6、be a more hypothetical group:,“How much of a reduction in symptomatic days could a person expect if treated with a new antiviral for flu?”,6,6,第6页,总体,样本和个体,实际上,我们不可能去研究总体中每一个对象。,所以,我们研究一个,样本,并将其推广到整个人群。,样本量,是样本中,个体,数目(而不是对每个研究对象测量指标数目!),好研究设计能帮助我们得到一个 代表性好样本。,好统计分析能帮助我们取得关于总体问题答案。,6,7,第7页,例子:HCC裸鼠转移
7、模型,免疫重建,对照组,CD3,31.5%,14.2%,CD4,XX,XX,CD8,XX,XX,*2个水平:裸鼠 细胞,6,8,第8页,今天主题,总体,样本和个体,资料类型:Continuous vs.categorical,怎样描述资料?统计量 和图,测量集中趋势和离散趋势,标准误和95%可信区间,依据数据选择适当统计方法,诊疗试验评价,6,9,第9页,数据类型,计量资料 Quantitative:“how much?”,连续变量,:年纪,体重,身高,血压,实际数值,:家庭儿女数,住院天数,分类资料 Categorical:“what type?”等级变量:肿瘤分期(I,II,III);好
8、中 差名义变量:男/女;健康/生病;ABO血型,6,10,第10页,数据类型,数据类型转换,计量数据可转换成份类数据:,normal(value)vs.abnormal;,“young,middle-aged,old”,将连续变量转换成等级变量降低了资料信息量,从而造成统计学检验敏感度或把握度下降,6,11,第11页,今天主题,总体,样本和个体,资料类型:Continuous vs.categorical,怎样描述资料?统计量 和图,测量集中趋势和离散趋势,标准误和95%可信区间,依据数据选择适当统计方法,诊疗试验评价,6,12,第12页,Notes:,vertical axis can be
9、 count or percent,in the above example,counts do not add to 74 individuals can have multiple risk factors,tabular presentation may be more parsimonious for such data,N=74,分类资料统计描述,计数,百分比,6,13,第13页,分类数据统计描述,组成比,率,百分比 vs 率,标化,6,14,第14页,下面是一组年纪数据(11例),21,32,34,34,42,44,46,48,52,56,64,年纪是一个计量变量,所以假如用条图就
10、不适当。我们更感兴趣是,年纪分布,一些特征:,年纪分别中心点在哪里?如平均数,年纪变异又是怎样?,是不是有些数据跟绝大部分数据差得很多(outliers),借助视觉工具帮助我们回答这些问题.,定量数据统计描述,6,15,第15页,计量数据统计描述,图表,1.Stem and Leaf plot,2.Histogram,3.Boxplot,数字,1.Location-mean,median,mode.,2.Spread-range,variance,standard deviation,percentile,3.Shape-skewness,*例外:生存资料描述,6,16,第16页,We cou
11、ld group the data and tally the frequencies:,But why“hide”the details?Instead,well use the 10s place as stems and the units as leaves:,20:X,30:XXX,40:XXXX,50:XX,60:X,2*|1,3*|244,4*|2468,5*|26,6*|4,Stem and Leaf Diagram,stem&leaf plot,For small datasets,6,17,第17页,Examples,平均数,方差,中位数,百分位数,outlier,6,18
12、,第18页,今天主题,总体,样本和个体,资料类型:Continuous vs.categorical,怎样描述资料?统计量 和图,测量集中趋势和离散趋势,标准误和95%可信区间,依据数据选择适当统计方法,诊疗试验评价,6,19,第19页,集中趋势,算术平均数:,几何平均数,中位数,6,20,第20页,平均数和中位数比较,Mean is sensitive to a few very large(or small)values-“outliers”,Median is“resistant”to outliers,Mean is attractive mathematically,50%of sa
13、mple is above the median,50%of sample is below the median.,6,21,第21页,离散趋势,Variation is important!,6,22,第22页,离散趋势,方差,标准差,百分位数:,IQR=Q,.75,-Q,.25,6,23,第23页,今天主题,总体,样本和个体,资料类型:Continuous vs.categorical,怎样描述资料?统计量 和图,测量集中趋势和离散趋势,标准误和95%可信区间,依据数据选择适当统计方法,诊疗试验评价,6,24,第24页,标准误和95%可信区间,描述样本:平均数,标准差,?总体:,为了预计
14、总体平均数,需要计算,标准误,标准误标准差,/,样本量,总体均数95CI:,样本平均数,1.96*,标准误,论文中惯用,6,25,第25页,标准差 vs均数标准误,(when do you use one,but not the other?),标准差,用于描述:量化样本均数周围变异.,当确定两个样本是否来自于同一总体时,标准差是一个主要统计量。,Central limit theorem,;“同一总体中样本均数呈正态分布”,样本均数,标准误,用于样本均数预计总体均数。,标准误是一个主要统计量,用于计算样本均数可信度,取决于标准差和样本量。但实际上二者并不独立,当样本量增加时,标准差往往降低,
15、。,6,26,第26页,正态分布,(basis of statistical inference for many populations ),Mean=median=mode.all=same value in the distribution,remember,:,68,.3%of data is between -1.00 s.d.and +1.00 s.d.,95.0,%“-,1.96,s.d.and +,1.96,s.d.95.5%“-2.00 s.d.and +2.00 s.d.99.7%“-3.00 s.d.and +3.00 s.d.,6,27,第27页,今天主题,总体,样本和
16、个体,资料类型:Continuous vs.categorical,怎样描述资料?统计量 和图,测量集中趋势和离散趋势,标准误和95%可信区间,依据数据选择适当统计方法,诊疗试验评价,6,28,第28页,推断性统计,推广结论:,样本总体,评价证据强度,比较,预测,6,29,第29页,计量资料统计方法,正态分布,非正态分布,配对资料(2组),配对t检验,符号检验,符号等级检验,成组比较 (2组),成组比较t检验,Wilcoxon Mann&Whitney,中位数检验,配伍组比较,随机区组方差分析,非参数配伍组比较M检验,多组比较,完全随机设计方差分析,非参数多组比较H检验,6,30,第30页,列
17、联表分析,行,名义变量,等级变量,名义变量,普通联络:,Pearsons 2,行平均得分:,(趋势分析),等级变量,行平均得分:,2,(趋势分析),相关分析:,cmh:,2,列,*四格表是全一致,6,31,第31页,Make predictions:回归分析,应变量:,普通定量变量 线性分析,等级或名义变量Logistic 回归,时间变量 Cox回归,6,32,第32页,Descriptive epidemiology:pattern of occurrencePrevalence of HIV+and community Mosquito index,r =.83 r-squared=.92
18、 *,p .001 p .001 *,*,*,*,*,20,15,10,5,0,0 2 4 6 8 10 12 14 16 18 20 22,Index of community mosquito infestation,HIV+,6,33,第33页,今天主题,总体,样本和个体,资料类型:Continuous vs.categorical,怎样描述资料?统计量 和图,测量集中趋势和离散趋势,标准误和95%可信区间,依据数据选择适当统计方法,诊疗试验评价,6,34,第34页,诊疗试验评价,试验设计,6,35,第35页,诊疗试验设计,6,36,第36页,诊疗试验评价,金标准,有病,金标准,无病,试
19、验,a,b,试验,c,d,敏感度a/a+c,特异度d/b+d,阳性预测值a/a+b,阴性预测值d/c+d,阳性拟然比敏感度/1特异度,阴性拟然比1敏感度/特异度,6,37,第37页,医学论文中通常报道哪些?,大多数研究报道,平均数,(正态)或,中位数,(非正态),有些研究报道标准差和/或标准误。Be careful!有时会看到图中有一个error bar,could be either.,假如资料非正态(偏态,多峰,尾巴很长或很短等),往往报道中位数和百分位数,而不是均数和标准差.,写文章时一定有根根本研究所要回答问题:,Do you want to ask about the average
20、 or typical person?Or do you want to figure out how unusual your patient might be?,6,38,第38页,通常流行病学(科学)路径,1.确定一个,问题,:clinical suspicion;case series;review of medical literature,2.组织一个,假设,(asking the right question);good hypotheses are:Specific,Measurable,and Plausible,3.,检验假设,(assumptions vs.type of
21、 data),4.再,验证,always,Question,the VALIDITY of the result(s):Chance;Bias;and Causality,6,39,第39页,结论准确性,Chance,:role of,random,error in outcome measure(s),(p-value;power of the study and the confidence interval),-largely determined by sample size,Bias,:role of,systematic,error in outcome measure(s),Se
22、lection,bias -subjects not representativ,Information,bias -error(s)in subject data/classification,Confounding,-3rd variable(causal)assoc.w/both X and Y,6,40,第40页,oZr%u(x+B2E5H9KcOfRiUmXp#s&v)z0C3F7IaLdPgSjVnYq$t*w-A1D4G8JbNeQhTlWoZr%u(y+B2E6H9KcOfRjUmXp!s&v)z0C4F7IaMdPgSkVnZq$t*x-A1D5G8KbNeQiTlWo#r%
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33、C3F6IaLdOgSjVmYq!t*w-z1D4G7JbMeQhTkWoZr$u(x+B2E5H9KcNfRiUmXp#s&v)y0C3F7IaLdPgSjVnYq$t*w-A1D4G8JbNeQhTlWoZr%u(y+B2E6H9KcOfRiUmXp!s&v)z0C3F7IaMdPgSkVnYq$t*x-A1D5G8JbNeQiTlWo#r%u(y+B3E6H9LcOfRjUmYp!s&w)z0C4F7JaMdPhSkVnZq$t*x-A2D5G8KbNeQiTlXo#r%v(y+B3E6I9LcOgRjUmYp!t&w)z1C4F7JaMePhSkWnZq$u*x+A2D5H8KbNfQ
34、iUlXo#s%v(y0B3E6I9LdOdOgRjVmYq!t&w-z1C4G7JaMePhTkWnZr$u*x+A2E5H8KcNfQiUlXp#s%v)y0B3F6IaLdOgSjVmYq!t*w-z1D4G7JbMeQhTkWoZr$u(x+B2E5H9KcNfRiUlXp#s&v)y0C3F6IaLdPgSjVnYq!t*w-A1D4G8JbMeQhTlWoZr%u(x+B2E6H9KcOfRiUmXp!s&v)z0C3F7IaMdPgSkVnYq$t*x-A1D5G8JbNeQhTlWo#r%u(y+B2E6H9LcOfRjUmXp!s&w)z0C4F7IaMdPhSkVnZq$t
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38、2D5H8KbNfQiUlXo#s%v(y0B3F6I9LdOgRjVmYq!t&w-z-z1C4G7JbMePhTkWnZr$u(x+A2E5H8KcNfRiUlXp#s%v)y0C3F6IaLdOgSjVnYq!t*w-z1D4G7JbMeQhTkWoZr$u(x+B2E5H9KcNfRiUmXp#s&v)y0C3F7IaLdPgSjVnYq$t*w-A1D4G8JbNeQhTlWoZr%u(y+B2E6H9KcOfRiUmXp!s&v)z0C3F7IaMdPgSkVnYq$t*x-A1D5G8JbNeQiTlWo#r%u(y+B3E6H9LcOfRjUmYp!s&w)z0C4F7JaMdPhSkVnZq$t*x-A2D5G8KbNeQiTlXo#r%v(y+B3E6I9LcOgRjUmYp!t&w)z1C4F,6,41,第41页,