Classes 24-25 Cross-Section Studies Flashcards
Cross-Sectional Studies
Observational, descriptive/analytical studies that examine relationships of health/disease to other variables of interest at the same time
a.k.a. Prevalence study; large pop. size
Entire population or a subset is selected for study
“Snap-shot” in time
If a study has the word “National” in its title, it is most likely what type of study?
Cross-sectional study
Cross-sectional studies seek ______, not causation
Associations
By repetition in different time periods, cross-sectional studies can be used to measure:
Change/Trends
Most cross-sectional studies are ____ of or ____ related to different aspects of US population.
Surveys of or databases
Cross-Sectional Studies (Person, Place, Time)
Studies all of persons with the variables of interest (Person)
Defines the geographical boundary for the study (Place)
Studies disease and risk factor patterns over a specified time period (Time)
Advantages of Cross-Sectional Studies
Fairly quick and easy to perform for the researcher using the data
Useful for determining prevalence, measuring current health status & planning for health services across the pop., & evaluating difference in sub-groups within the pop.
Disadvantages of Cross-Sectional Studies
Prevalent cases may represent survivors
Difficult to study diseases of low frequency
Problems in determining temporal relationship of presumed cause and effect
2 Cross-Sectional Approaches
- Collect data on each member of the population (more frequently utilized in city/state-level evaluations)
- Take a sample of the population & draw inferences to the remainder (more frequent approach for US-level data)
Probability Samples
Most common
Every element in the pop. has a known (non-zero) probability of being included in sample
Simple Random Samples
Stratified Random Samples
Simple Random Samples
Obtain list of population names
Assign #s to names and use random # to generator to select samples
Stratified Ransom Samples
Mutually exclusive strata (categories) - age or socioeconomic groups
Divide population into relevant subgroups (take simple random sample from each subgroup)
Some studies oversample certain subgroups such minotities
“Systemic” or “Convenience” samples
Not really completely random or fully probabilistic
Decide on what fraction of population is to be sampled and how they will be samples
Ex. All persons whose last name begins with “M-Z”
Two common major approaches to collection of new information in Cross-Sectional studies
Questionnaires/Surveys Physical assessments (which might involve laboratory, clinical, or psychological tests)
Examples of Cross-Sectional Surveys from NCHS
National Health and Nutrition Examination Survey (NHANES)
National Health Interview Survey (NHIS)
National Ambulatory Medical Care Survey (NAMCS)
National Hospital Care Survey (NHCS)
Behavioral Risk Factor Surveillance System (BRFSS)
National Health and Nutrition Examination Survey (NHANES)
Assesses the health & nutritional status of adults & children
Survey sample is selected to represent the US population of all ages
Oversamples persons greater than or equal to 60 years old, Blacks/African Americans, & Hispanics
National Health Interview Survey (NHIS)
Principal source of info on health of the civilian, non-institutionalized population (all ages)
Data are collected through a personal household interview (Broad range of health topics)
Consists of a set of core questions that remain largely unchanged & set of supplements used to respond to public health date needs as they arise
National Ambulatory Medical Care Survey (NAMCS)
Designed to meet the need for objective, reliable info about the provision and use of ambulatory medical care services in the US.
Based on sample of visits to non-federal, office based physicians primarily engaged in direct patient care.
National Hospital Care Survey (NHCS)
Designed to describe national patterns of healthcare delivery in non-federal hospital-based setting, including discharges from inpatient departments & institutions, & visits to emergency departments, outpatient departments, & ambulatory surgery centers.
Integrates National Hospital Discharge Survey, National Hospital Ambulatory Medical Care Survey, and Drug-Abuse Warning Network.
Behavioral Risk Factor Surveillance System (BRFSS)
State-based system of telephone health surveys that collects info on health risk behaviors, preventative health practices, & health care access primarily related to chronic disease & injury.
>500,000 adults interviewed by telephone
Youth BRFSS conducted by questionnaire in schools
Difference between randomization and random selection
Randomization is the group allocation; prevents bias; trying to make groups equal
Random selection is an unbiased way to reach in a get participants for a study; when you have too many to pick from; sampling technique
