Lecture 12 Flashcards
Why are they called cross-sectional studies?
Because the information gathered represents what is occurring at one point in time or time-frame
What is a cross-sectional study?
Observational, descriptive studies that examine relationships of health/disease to other variables of interest at the same time (prevalence study)
Does a cross-sectional study show association or causation?
Causation
T/F: Most cross-sectional studies are “surveys” of US poplulation from different perspectives.
True
What are advantages of a cross-sectional study?
Quick and easy
Almost always exempt from IRB review
What are cross-sectional studies useful for?
Determining prevalence of disease and risk factors
Determining frequency for a defined population
Measuring current health status and planning for health services for large population
Evaluating differences in sub-groups within populations (at a given time)
What are disadvantages of cross-sectional studies?
Prevalent cases may represent survivors
Difficult to study diseases of low frequency
Problems in determining temporal relationship of a presumed cause and effect
What are the 2 approaches to cross-sectional studies?
Collect data on each member of the population
Take a sample of the population and draw inferences to the remainder
What are the 2 types of sampling schemes?
Probability and non-probability samples
What are the 4 probability samples?
Every element in population has non-zero probability of being included in sample (used for most cross-sectional studies)
Simple random samples
Systematic samples
Stratified samples
What is a simple random sample?
Put al lnames in a box and draw out samples needed
What is systematic samples?
Not completely random
Decide what fraction of population is to be sampled
EX: Last name “m-z”
What are stratified samples?
Mutually exclusive and exhaustive strata—age or socioeconomic groups
Divide population into relevant subgroups
What are non-probability samples?
Based on sampling plan that does not have a non-zero probability
(not good for cross-sectional studies because reliability of results cannot be evaluated)
What are the two major approaches to collection of new information?
Questionnaires/surveys
Physical assessments
What is NHANES?
National Health and Nutrition Examination Survey
Assesses health and nutrition of children and adults
What is NHIS?
National Health Interview Survey
Source of information on health of civilian, non-institutionalized population
Contains core questions that remain largely unchanged
What is NAMCS?
National Ambulatory Medical Care Survey
Designed to meet the need for objective, reliable information about the provision and use of ambulatory medical care
Based on sample of visits to non-federal, office-based physicians in direct patient care
What is NHAMCS?
National Hospital Ambulatory Medical Care Survey
Designed to collect data on utilization and provision of ambulatory care services in ER and outpatient departments
Based on visits to ER/outpatient departments of general hospitals
What is BRFSS?
Behavioral Risk Factor Surveillance System
State-based phone surveys collecting information on health risk behaviors, preventative health practices, & health care access primarily related to chronic disease injury
What are ecological studies?
Observational, descriptive studies that examine relationships of health or disease to other variable of interest in which population groups are the unit of study (rather than individuals)
What is the aim of an ecological study?
Identifying and explaining association between groups and their environments
T/F: Ecological studies inform researchers about the forces which act on whole populations, which may be in conflict with those that act on individuals
True
What are ecological studies assessing the correlation between?
Exposure and disease rates among different populations
What should be done when one or more measures used involves rates-by-age?
Those rates should be age-adjusted
What are the 3 common fallacies of ecological studies?
Ecological fallacy, Atomistic fallacy, & Homogeneity fallacy
What is the ecological fallacy?
Association found with aggregate data may not apply to individuals
What is the atomistic fallacy?
Studies of individuals are prone to the opposite of the ecological fallacy
What is the homogeneity fallacy?
Misrepresentation of population data from heterogeneous populations
