Karteikarten
Cross sectional
Karten in diesem Stapel (67)
- 1In an experimental epi study, the investigator___randomyl assigns treament (esposure ) to study participants, it has adv and disadv
- 2In an observational study, the investigator can only___observe outsomes associates with the individual esposures experinced by the study participants.
- 3In contrast to a RCT, observational studies are notassighned
- 4Most epid. studies areobservational
- 5Epid studies are divided intoexperimental and observational
- 6Observational studies are divided intoecological, cross sectional, case control and cohort
- 7Study designs can be __hybrids and are not necessarily mutually exclusive
- 8Ecological aretime- trend (past) OR Present period/ aggregate data (present), Historical data (yes/no)
- 9In a cross sectional:Exposure and disease (present), no historical data
- 10In a case controlDisease (presnt) and looks back to exposure (past), no hisorical data
- 11In a Retrospective cohortdisease is in the present and looks back to exposure (past), There is historical data
- 12Propective cohortExposure in the present and disease in the future, no hissotical data
- 13which has historicla dataecological (yes/no) and Retorspective cohort
- 14Who has in the pastEcological, case control and retorspective
- 15Who has in the futreprospective cohort
- 16Ecological studies are associated between anexposure and in outcome
- 17In ecological studies the unity of analysis ispopulation or groups of people rather than individual
- 18In ecological, each group is clasified with respect toexposure aans disease status
- 19In ecological studies:what is missing on the joint distribution variables within each group (2x2 table)individual level data is missing
- 20Ecological studies usually describe groups defined bygeography and/or time
- 21Aggregate measures aresummers of observations derived from individuals in each groups: % of pop over 65
- 22Environmental measure:physical characteristics of the place in which members of each group live or work: concentration of airborne mercury in Santa Cruz
- 23Global Measures areattributes of groups for which there is no distinct analog at the individual level:gun control
- 24What is soem rationale for ecological studies1. Low cost and convenience 2. Measurement limitations of individual studies 3. Design limitation of level studies 4. Useful for generating hypothesis
- 25Ecological studies: Low cost and convenienceStudies often involve data from population registries, vital records and other secondary sources (dont need to collect data)
- 26Ecological studies: Measurment Limitations of individual-level studiesoften difficult to assess environmental exposure for individuals
- 27Ecological Studies: Design limitations of individual level studiesminimal variability in exposure within a given study are: intra group variabilty is small, but inter group variabilty is large
- 28Study desighns for ecological studies1.
Multi group 2. Time Trend 3. Mixed Study - 29Eco: Multiple Group:same time,differnt group/region; Exploratory: Compares disease rates of different groups (migration studies)
- 30Multi Group can also beAnalytic: Compare exposure and disease by country, dietary fat intake and breast cancer
- 31Multi Group has 2 typesexploratory and Analytic
- 32Eco: Time trenddiffernt time, same group / region
- 33Eco: Time TrendExploratory: age-period-cohort analysis
- 34Eco:Time trendAnalytic: Compare changes in exposure and disease over time in the UK, tobacoo consumption and lung cancer from 1900-1950
- 352 types of time trend eco studiesExploratory and Analytic
- 36Eco : Mixed studiesincorporate both desighs
- 37The dietary fat intake and breast cancer by country ( incidence rate per year vs per capital supply of fat calories ) are examples ofmultiple group (analytic) ecological study
- 38Tobacco use and lung cancer in the UK ( death rate cancer of the lung per million and consumption of tabacco and cigarette lbs per person vs yearexample of time trend (analytic) ecological study
- 39Male circumcision are examples ofvariations in magnatude of HIV epidemic in Africa are striking
- 40The purpose pg the male hiv circum and HIV was toexplor the realtionship between HIV and seroprevance and proportion of uncircumcised males in african countries
- 41Why should you conduct the ecological study of male circum and HIVto explose a potential hypothesis using exsisting data
- 42The study design for the male circum and hivexample of a multi group
(analytic)eco study, examined prevalence of male circumcision an d hiv in 140 locations/41 countires - 43What are some study limitation of the eco studythe population level correlation between male circumcision and hiv prevalence does not prove a cause and effect relationship
- 44What are potential confounders of the associationplaces of introduction of HIV (uncir//cirm), Differences in sexual behavior(#of sexual partners, use of protection), Differnce in religion and practices (christians vs. muslims), methodologic problems
- 45in Ecological studies there aremethodologic problems
- 46method. propblem: Ecological falacy (bias) occurs whenan aggregate level association is inferred as an individual level association
- 47Ecological bias can arise fromConfounding by group
- 48Confounding by group isunique to ecological studies:1. extraneous risk factors are differently distributed across groups 2. exposure effect on disease risk differs at the individual and aggregate levels
- 49Confounding by Group examplesusicde rates in Catholic vs Prtoestant
- 50The fit of the ecological regression model provides no indication ofpresence , direction, or magnitude of bias
- 51excelent model fit does notpreclude ecological bias
- 52what bias could exist in the ecological study of suicidemeans of resolving ecological bias
- 53If possible in an ecolog we must utilizesmaller unity to make groups more homogeneous with respect to expose
- 54Associations may ___ be cusual in eco studiesNOT
- 55Association may not be causal becuase1. could be due to a third factor or intermediate variable 2. limited for testing etiologicl hypothesis 3. Temporal ambiguity
- 56Temporal ambiguity is true forcross sectional and ecolgical studies
- 57Issues with eco stidiesCollinearity and association may not be causal
- 58Collinearity in eco stuidiescertain predictors such as sociodemographics and environmental factors , tend to be highly corelated
- 59Colinearity is more inecological studies and individual level studies
- 60Cross sectional examineslooks at preset and examines disease between exposure and disease at a single point in time
- 61In corss sectional: individual isunit of analysis
- 62Study population is selcted froma single target populatio withought regard to 1. exposure OR 2. disease status
- 63Cross section is asnapshot in time aka a prevalence study
- 64Advantages of Cross sectional1. quick and inexpensive 2. useful foe describing characteristics of the target population 3. Findings may be more representative of general population than other epi studies 4. Association are useful for hypothesis generation
- 65Cross sec: Quick and inexpensive:useful for health planning and best suited for disease of slow onset and long duration
- 66Cross sectiona studies: Usefull for describing chracteristics of the target pop:can provide estimates of disease and exposure
- 67Cross sectiona Disadvantages:1. cannot establish a temporal relationship 2. inefficient when exposure or outcome are are 3. may be useful for etologic (causal) research (can only estimate prevalence not incidence the risk of death
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- college Epid (Final) Karteikarten am Cross sectional, erstellt von maxytrejo1 am 13/05/2014.
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- maxytrejo1
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