Chapter 6: Study Designs: Ecologic, Cross-Sectional, Case-Control Flashcards
Association
A linkage, connection, or statistical dependence between (among) two or more factors.
Case-control study
A study that compares individuals who have a disease with individuals who do not have the disease in order to examine differences in exposures or risk factors for the disease.
Cross-sectional study (also, prevalence study)
A type of descriptive study (e.g., a population survey) designed to estimate the prevalence of a disease or exposure.
Ecologic comparison study
Type of research design that assesses the correlation (association) between exposure rates and disease rates among different groups or populations over the same time period. The unit of analysis is the group.
Ecologic fallacy
A misleading conclusion about the relationship between a factor and an outcome that occurs when the observed association obtained between study variables at the group level does not necessarily hold true at the individual level.
Ecologic trend study
Type of study that examines the correlation of changes in exposure and changes in disease over time within the same community, country, or other aggregate unit.
Experimental study
Research design in which the investigator manipulates the study factor and randomly assigns subjects to exposed and nonexposed conditions.
Exposure
A causal factor or variable; to be in contact with a causal factor such as a disease agent or toxic chemical.
Nonprobability sample
Type of sample in which the population does not have a nonzero probability of being inlucded in the sample (e.g., quota samples and judgmental samples).
Observational study
A type of research design in which the investigator does not manipulate the study factor or use random assignment of subjects. There is careful measurement of the patterns of exposure and disease in a population in order to draw inferences about the distribution and etiology of diseases. Observational studies include cross-sectional, case-control, and cohort studies.
Odds ratio
Measure of association between frequency of exposure and frequency of outcome used in case-control studies. The formula is (AD)/(BC), where A is the number of subjects who have the disease and have been exposed, B is the number who do not have the disease and have been exposed, C is the number who have the disease and have not been exposed, and D is the number who do not have the disease and have not been exposed.
Probability sample
Type of sample in which every element in the population has a nonzero probability of being included in the sample (e.g., simple random sample).
Quasi-experimental study
Type of research design in which the investigator manipulates the study factor but does not assign subjects randomly to the exposed and nonexposed groups.
