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PHC 6000: Designs

Introduction to epidemiology: Study designs

QuestionAnswer
What kind of studies can be used to differentiate between environmental and genetic characteristics? Migration studies
In which types of studies, the unit of analyses are usually populations or groups rather than individuals? Correlational studies ~ ecological studies
What is ecological fallacy? An error of deduction that involves deriving conclusions about individuals solely on the basis of an analysis of group data.
What situation can occur when a researcher or analyst makes an inference about an individual based on aggregate data for a group? Ecological fallacy
What are cross-sectional studies also called? Prevalence studies
What is the hierarchy of study samples? Target population > sampling population > sample
What are the weaknesses of a cross-sectional study? -No cause-effect -No temporality -Prevalent cases are survivors -Not suitable for rare or short duration diseases -Disease process may alter exposure
What are the strengths of a cross-sectional study? -Study multiple outcomes & exposures -Help assess health needs and planning -May generate new hypotheses -Short duration/low cost
Aspirin is prescribed for heart disease. In an observational study, it may be incorrectly seen as a risk factor for heart disease. What is this an example of? Disease process may alter exposure
What is the outcome measure of cross-sectional studies? Prevalence ratio
What is the outcome measure of case-control studies? Odds ratio
What is the outcome measure of cohort studies? Relative risk
Why is the outcome measure of case-control studies not a measure of risk? We already have the outcome at the outset of the study
What are the strengths of a case-control study? -Good for rare diseases -Can test many hypotheses with respect to one outcome -Requires short time when outcomes are delayed -Cheap
What are the weaknesses of a case-control study? -Subject to bias (selection, information) -Indirect estimate of the Relative Risk -Temporality not clear -Not good for rare exposures -Multiple outcomes cannot be studied -Reverse causation is a problem in interpretation -Ca/co selection troublesome
What are the strengths of a cohort study? -Can look at many outcomes with respect to one exposure -Measures risk -Suitable for rare exposures -Direct measurement of incident -Addresses temporality -Minimizes recall bias -Allows for calc of incidence of diseases in exposed and unexposed
What are the weaknesses of a cohort study? -Costly/time consuming -Not suitable for rare disease -Loss to follow-up -Can be very time consuming if latent period is long -Changes over time in diagnostic methods -Nonparticipation bias (selection bias)
What are the 3 domains of person characteristics? Demographic, socioeconomic, and behavioral
What causes individual variation in disease occurrence? Can be due to difference in exposure, susceptibility, or both
What is the purpose of a case report? Documents unusual medical occurrences that can represent the first clues in the identification of new diseases or adverse effects of exposures
What are case series? Collections of individual case reports
What are correlational studies also called? Ecological studies
How are correlational studies used? Measures representing characteristics of the entire population are related to factors of interest
What is the unit of analyses for ecological studies? Populations or groups
It is seldomly possible to evaluate causal relationships from observed associations in which type of study? Correlational
In cross sectional studies, when are exposure and disease assessed? Exposure and disease are assessed simultaneously
What is the reverse causality problem in determining cause and effect? The problem is when the assumption is A causes B when the truth may actually be that B causes A. Which came first?
What are descriptive studies typically used for? Characterizing the distribution of disease within a population and hypothesis generation about the causes of disease occurrence in the population
What are analytic studies typically used for? Identifying possible causes for the occurrence of disease (risks)
What are experimental studies typically used for? To test new treatments or interventions
What types of studies asks questions to generate hypotheses? Descriptive studies
What do descriptive studies provide data on? Who? Where? When? = Person. Place. Time.
In this type of study, data mostly is aggregated and was previously collected for a purpose unrelated to the study. Ecological study
What are two types of ecologic studies? 1) Comparative 2) Time trends
What are comparative ecological studies? Studies that examine an exposure-disease relationship between groups at one point in time
What are time trends ecological studies? Studies that examine an exposure-disease relationship over several time points in a single group
What can ecologic variables summarize? Individual attributes, environmental attributes, and global variables
These types of studies usually describe groups defined by geography and/or time. Ecologic
When are ecologic studies most appropriate? This study design is often appropriate for studying broad social and cultural processes (e.g., poverty, laws/policies, access to care, environmental factors) or when population-level variables are of interest
In this type of study, the joint distribution of risk and outcome is often unknown Ecologic
Why is the joint distribution of risk and outcome often unknown in correlational studies? Existing data sources are often compiled independently
An association at the aggregate level does not guarantee an association at the individual level. (T/F) True
In which type of study are groups identified on the basis of the outcome? Case-control
Which type of study design requires smaller sample size, ca/co or cohort? Case-control
This type of study design is good for rare outcomes or outcomes of long latency. Case-control
Which study design is best suited to the study of diseases for which medical care is sought (e.g., cancers, hip fracture)? Case-control
Which type of study should be the first approach to testing of a hypothesis (useful for exploratory study of multiple variables looking for clues)? Case-control
This type of study is susceptible to bias and confounding and appropriate control group can be difficult to find Case-control
What is the strongest observational design for establishing a cause and effect relationship? Cohort
What type of study allows for calculation of incidence of diseases in exposed and unexposed individuals? Cohort
What type of study allows direct calculation of relative risk? Cohort
What type of study is efficient for study rare exposures? Cohort
What type of study is efficient for study rare outcomes? Case-control
Created by: AlneciaPHS