3横断面研究.ppt

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,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Company name,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Company Logo,*,Click to edit Master title style,*,单击此处编辑母版标题样式,研究生课程,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,研究生课程,*,Click to edit Master title style,1,Ch3 Research Methods of Epidemiology(,),Descriptive study,2,Questions,：,常住居民健康状况（常见,/,多发病、亚健康等）？,疾病的早期筛检,(,screening,),及诊断,(,diagnose,),？,医院感染,(,hospital infection,),发生情况（分布特征）？可能存在的主要影响因素？采取措施后效果如何？,如何合理安排医院各科的床位、医护人员等？,患者对医院服务,(,hospital service,),的满意程度？,某慢性病,(,chronic disease,),对患者生活质量,(,quality of life,),的影响？,关于社区获得性肺炎,(,Community-acquired pneumonia,),？,3,Example,4,。,5,根据日常记录资料或通过特殊调查所得到的资料（包括实验室检查结果），对被研究人群的疾病或健康状况进行三间分布特征描述的研究，它是分析性研究的基础。,Concept of descriptive study,研究生课程,6,Commonly used data,demography data,death data,disease data,other,6,研究生课程,7,【Characteristic】,属观察性研究,observation,无须事先设立对照组,no control,不能分析暴露与效应之间的因果联系,cannot analysis causal association,8,【Category】,横断面研究,cross-sectional study,生态学研究,ecological study,常规历史资料分析,analysis of,history data,个案调查,case investigation,病例报告,case report,9,概念,特点,研究目的与用途,种类,设计与实施,优点与局限性,横断面研究,cross-sectional study,10,横断面研究又称现况研究或患病率研究,（,Prevalence study,）,是对某人群在某一时间断面的有关因素及健康状况进行的调查研究，从而客观反映有关因素与疾病的分布及二者之间可能存在的关系。,一、,概念,11,属观察性、描述性研究,无事先设立的对照组,只能反映某一特定时点的情况,因果并存，不能确定因果关系,二、特点,12,了解疾病或健康状况的分布特征,了解分布特征与疾病之联系，提供因果线,索或建立病因假设,考核防治措施效果（重复横断面研究）,了解疾病现况，合理分配卫生资源,衡量国家或地区的卫生水平和健康状况,进行疾病监测，了解疾病的长期变化趋势,早期发现病人或高危人群,三、研究目的和用途,13,四、种类,普查,（,Census,）,调查特定时点或时期、特定范围内的全部人群,(,总体,),抽样调查,（,Sampling survey,）,随机抽样，调查特定时点、特定范围人群的一个代表性样本，以样本统计量估计总体参数所在范围,14,1,、普查（,census,）,目的：,早期发现和治疗疾病,了解疫情，早期预测疫情,建立生理指标的正常值,了解疾病或生理标准的地区、年龄、性别、民族、职业分布，为进一步研究提供线索,15,优点：,信息全面，准确性好,缺点：,花费大，精确性难以保证；当患病率低、,或无简易敏感的诊断方法、无切实有效,的治疗方法时不适用,适用症：,应用原则,(,同筛检,),成本,-,效益分析后再确定,16,应用原则：,检测手段灵敏、可靠,被调查疾病的患病率较高（或是当地主要卫生问题）,疾病进行性发展，自然史比较明确,有较长的领先时间,早期治疗有效，可明显改善预后,17,2,、抽样调查（,sampling survey,）,优点：,快速、高效、花费少、较为精确,缺点：,信息存在误差（随机或,/,和系统的）,准确性不如普查；不适用于患病率低、,变异较大的情况；设计、实施及资料,分析较复杂,适用症：,快速评价,应用原则：,样本具有代表性和足够量；调查方,法可靠,18,（一）研究目的,（二）研究类型与方法（包括抽样方法）,（三）研究对象及样本含量,（四）资料收集,（研究指标，,调查表设计,）,（五）偏倚与控制,（六）,资料分析,（统计方法、分析提纲）,（七）,可行性分析（人力、物力、财力等）,五、设计与实施,19,（一）明确研究目的（二）研究类型和方法,由研究目的决定研究类型和方法,观察法与实验法,普查与抽样调查,抽样方法,20,抽样方法,非随机抽样,non-random sampling,选择样本时，加入研究者,主观因素,，使总体中每个个体被抽取的机会不均等。,随机抽样,non-random sampling,遵循,随机化,原则，保证总体中每一个个体都有同等机会被选入作为研究对象。,21,随机抽样方法：,单纯随机抽样,（,simple random sampling,）,系统抽样,（,systematic sampling,）,分层抽样,（,stratified sampling,）,整群抽样,（,cluster sampling,）,多级抽样,（,multi-stage sampling,）,随机误差与系统误差（偏倚）,样本大小的估计,22,目标人群,target population,纳入标准,样本大小估计,主观因素：,值和（,1-,）值,抽样方法,客观因素：研究指标的变异程度,预计值（如患病率，阳性率等）,（三）,研究对象,23,计量资料样本大小估计公式,计数资料样本大小估计公式,t:,统计学上的,t,值,d:,容许误差,P,：某病现患率,Q=1,P,24,（五）资料收集,通过测定或检查的方法收集,尽量采用客观、定量的研究指标和准确可靠的检测方法。,直接用调查表询问研究对象,25,（六）偏倚与控制,偏倚是指调查或研究结果与真实情况不符，或样本统计量不能代表总体参数所在的范围，是一种系统误差。,产生原因：,主观选择研究对象,任意变换抽样方法,调查对象不合作或因种种原因拒绝参加,调查到的对象均为幸存者，无法调查死亡者,回答不准确或回忆不清,测量误差,26,严格遵照抽样方法要求，确保随机化原则,提高研究对象的依从性和受检率,正确选择测量工具和检测方法,培训调查员，统一标准和认识,作好资料的复查复核工作,选择正确的统计分析方法，辨析混杂因素,偏倚的控制,27,（七）资料分析,检查资料的完整准确性，补缺、补漏，删除重复，纠正错误,对疾病或某健康状态按规定的标准归类核实,按不同空间、不同时间、不同人群描述分布特征和差异，进行显著性检验,可按是否暴露于研究因素或是否有病进行分组，从而进行比较分析,28,研究生课程,29,研究生课程,30,研究生课程,31,研究生课程,32,优点：,1,、样本来自人群，研究结果有较强的推广意义,2,、调查人群中有自然形成的同期对照，具有可比性,3,、可同时观察多种因素,4,、无医德问题,六、优点与局限性,33,缺点及局限性：,1,、疾病与因素同时存在，难以推断因果关系,2,、只能获得患病率，无发病率资料,3,、潜伏期或缓解期患者易被误诊而产生偏倚,4,、一般只适用于对慢性病的研究,5,、可产生选择性偏倚和信息偏倚,34,定义,目的,研究方法,优点,缺点,生态学研究,ecological study,Company name,35,描述性研究的一种,在群体水平上研究某种因素与疾病的关系,以群体为观察和分析单位,描述不同人群中某因素的暴露状况与疾病的频率，分析该暴露因素与疾病的关系,一、定义,Company name,36,提供病因线索，建立病因假设,评估人群干预措施的效果,二、目的,Company name,37,生态比较研究,ecological comparison study,观察不同人群或地 区某种疾病的分布，然后根据疾病分布的差异，提出病因假设,生态趋势研究,ecological trend study,连续观察不同人群中某因素平均暴露水平的改变和,(,或,),某种疾病发病率、死亡率变化的关系，了解变动趋势，比较暴露水平变化前后疾病频率的变化情况，判断某因素与某疾病的联系。,三、研究方法,Company name,38,经济，出结果快,提供病因未明疾病的病因线索,在个体剂量无法测量时，是唯一可供选择的方法,适用于研究因素暴露变异范围小，较难测量暴露与疾病的关系,人群干预措施的评价及估计疾病发展趋势,四、优 点,Company name,39,生态学谬误,ecological fallacy,难以控制混杂因素,存在多重共线性问题,难以确定因果联系,五、缺 点,Company name,40,个案调查,case investigation,对个别发生的病例、病家及周围环境进行的流行病学调查，多用于传染病及不明原因疾病的调查。,通过流调，了解分析传染来源、接触者以及可能的传播途径,掌握疫情，为控制疾病提供资料,如：,SARS,流调,Company name,41,病例报告,case report,对临床上某种罕见病的病例进行详细的介绍，以引起同行的关注。,有助于发现与识别新疾病或不良反应,如：,AIDS,的发现,有利于阐明疾病的发病与治疗机制,如：,“,氟烷肝炎,”,有助于阐明疾病的罕见临床表现,Company name,42,横断面研究医学文献的评价原则,1,、文献中欲阐述的问题是否可用横断面研究？,2,、是何种横断面研究？,3,、采用了何种抽样方法？调查对象的代表性如何？,4,、调查是否在同一个较短的时期内完成？,5,、是否考虑研究中可能出现的偏倚及解决办法？,6,、所采用的研究指标及统计分析方法是否正确？,7,、研究所得出的结论是否客观？科学性如何？,Company Logo,43,Questionnaire Design,44,Elements of Questionnaire Design,Identifying the questionnaire content,Writing or selecting questions to measure variables of interest,Constructing the questionnaire,45,A Questionnaire Is More than the Questions!,Other Elements,Opening/cover page,Instructions(skip patterns,probes,optional wording),Introductions to questions,Needed definitions and explanations,Transitions,46,Before Designing a Questionnaire,Decide the study,s,purpose,(aims,research questions,hypotheses),Identify the,variables,to be measured,Develop a preliminary,analysis,plan,Decide the,data collection mode,(e.g.,interview,paper/pencil,computer-assisted),47,Make a Variable List,Write or obtain questions to measure the variables,Use existing measures whenever possible!,Reliability and validity information may be available for existing measures,Allows comparison of results across studies,Allows estimation of trends,Adds to cumulative body of methodological experience with survey items,48,Objectives When Writing Questions,To get reliable and valid reports of respondents,experiences,Good survey questions provide consistent(reliable)and accurate(valid)measures,When 2 respondents are in the same situation they should answer the question the same way.,The answers to questions should correspond to what they are intended to measure.,49,Reasons Why Respondents Report Events with Less than Perfect Accuracy,They do not know the information,They cannot recall it,although they do know it,They do not understand the question,They do not want to report the answer in the context in which they are being asked it.,50,Considerations When Writing Questions,Type of question,Response formats,Question wording,51,Types of Questions,Open-ended questions,Close-ended questions,Ordered response categories,Unordered response categories,Partially close-ended questions,52,Open-ended Questions,Responses are not provided to the respondent.,Advantages:,Researcher does not need to know universe of possible answers,Respondent not influenced by specific alternatives suggested,Respondent can reveal what is most salient,Useful in exploratory work,Can be used to build rapport in interview,53,Open-ended Questions,Disadvantages:,Effort required of respondent,Respondents may vary in ability/willingness to articulate,Respondents may be reluctant to reveal detailed information or socially unacceptable opinions or behaviors,Large amount of information may be revealed,information may be vague or irrelevant,Difficulties in recording and in reducing and coding material,54,Close-ended Questions,A list of acceptable responses is provided to the respondent,Advantages:,Easier for respondent,Communicates same frame of reference to respondents,Standardization,Less variability in interviewer performance,Less time to administer and record response,55,Close-ended Questions,Disadvantages:,Need to know appropriate response categories in advance,Lack of spontaneity permitted respondent,Respondent may be forced into an unnatural frame of reference,May suggest response categories respondent has not thought of,Respondent may not feel as involved or motivated by questionnaire,56,Response Formats,Multiple categories that exhaust all meaningful answers and are mutually exclusive,During a typical work week(40 hours),how many hours do you spend on engaging in interpersonal relation:,_less than 10 hours,_10 to 19 hours,_20 to 29 hours,_30 to 39 hours,_40 hours or more,57,Ordered Response Formats,Response categories are ordered along a gradient.,Examples:,Strongly agree to strongly disagree(3 to 7 point scale;include or not include a neutral response category),Excellent,Good,Fair,Poor,Numerical rating scales,No,CompleteConfidence,Confidenceat All,_,1 2 3 4 5 6 7 8 9 10,58,Unordered Response Format,No single dimension underlies response categories.Respondent must evaluate each.,Example:,Which one of the following do you think is,most responsible,for the long waiting period in the emergency room of this hospital?(Choose only ONE answer.),Low staff morale,The low priority given to the emergency department by the hospital administration.,The low priority given to the emergency department by the medical staff.,The large number of people using the emergency room.,59,Partially Close-ended Questions,Answer choices are provided and respondents have the opportunity to create their own responses.,Example:,What is your position at this school?,Classroom teacher,Principal,Guidance counselor,Nurse,Other position(Please specify:_),60,Question Wording-DO,Make the wording clear and unambiguous,Use common vocabulary,Use vocabulary appropriate for your audience,Write questions like people talk not like people write,Only include one idea per question,Include both sides of the continuum in stem,Make the frame of reference appropriate and explicit,61,Question Wording-DO,Use techniques for enhancing recall,Shorten the reference period,Use landmarks to aid dating,Provide a helpful context,Provide cues to stimulate recall,Ask about typical behavior,62,Question Wording,DON,T,Use double-barreled questions,Where do you go to get information about HIV risk and to exchange needles?,When I get ill,I know it is because I have not been eating right or getting proper exercise.,Can you tell me when you last visited the clinic?,63,Question Wording,DON,T,Use leading questions,Do you agree that all children should be covered by health insurance?,With economic conditions the way they are these days,it really isn,t fair to have more than one or two children.,64,Question Wording,DON,T,Use double negatives,Lack of immunization for smallpox is not a problem in the U.S.,Most sex workers have little chance of not getting a sexually transmitted disease.,Use discriminatory or culturally insensitive words,husband/wife vs.partner,65,Question Wording,DON,T,Use incomplete wording,Age?What was your age on,your last birthday?,Reason last,What was the medical,saw doctor?,reason for which you most recently went to a doctor?,66,Question Wording,DON,T,Provide incomplete or overlapping response categories,Where have you received health care in the past 12 months?,_Student health,_UNC Hospitals,_Private MD in Chapel Hill,Use check-all-that-apply format,67,Question Wording,DON,T,Ask respondents to make unnecessary calculations.,Out of 100 students your age,how many to you think smoke cigarettes once a month?,Use loaded questions or loaded words,Have you ever shop lifted anything?,68,Practical Standardsfor Evaluating Questions,Is this a question that will mean the same thing to everyone?,Is this a question that people can answer?,Is this a question that people will be willing to answer,given the data collection procedures?,69,Constructing the Questionnaire:Putting the Questions In Order,Beginning,inviting,interesting,non-threatening questions,Middle,most important,put difficult and sensitive toward end,Closing,easy questions again,often routine,background,70,Question Order,Psychological not logical order,Chronological order where appropriate,Group questions by subject,Within a group,group questions with like response categories,General questions before specific,Be aware of order effects between opinion questions,71,Question Design,Include instructions,as needed,with questions-not at the beginning of the questionnaire,Clearly differentiate response categories from questions,Be consistent in placement of answer boxes,Ask one question at a time:don,t stack side-by-side,Number questions consecutively and simply from beginning to end,72,Other Elements,Title/cover page,General instructions,Identifiers(e.g.,respondent ID),Transitions,73,Summary,Decide what information(variables)is needed,Draft or obtain questions to elicit that information,Put questions in meaningful order,Add other elements of questionnaire,Pretest questionnaire,Repeat,74,调查表的设计,1,、原则：,必需项目一个不少，不需项目一个不多。,2,、类型：,开放式，即问答题或填空题形式,封闭式，即选择题形式,混合式，包含上述两种形式,3,、结构,封面信,指导语,调查问题和备选答案,调查者项目,75,4,、调查问题数量：,5,、调查问题的顺序：,先易后难,先客观后主观,先一般后敏感,同类问题在一起,6,、问题及答案设计,应围绕假设，避免无关问题,应符合实际情况,要具体化和可操作,应符合穷尽性和互斥性,76,吸烟情况调查表,1,、您曾吸过烟吗？吸过 不吸,2,、吸哪一种烟？有滤嘴 无滤嘴,3,、每天吸烟量：,支,4,、吸入深度：深吸 一般吸 不吸入,5,、您初次吸烟年龄是,岁,6,、如果已戒烟，戒了,年,7,、请回忆您的吸烟史：,偶吸,年,20,支,/,天,年,8,、共同生活中有谁吸烟：丈夫 妻子 子女 无,