Observational Study Designs Flashcards
what are major categories of quantitative designs?
non experimental
pre experimental
quasi experimental
true experimental
what are non-experimental designs?
methodologies where the researcher observes and analyzes naturally occurring situations without intervening or manipulating variables. Instead of actively changing variables, researchers simply observe and gather data from existing conditions.
what are types of non experimental designs?
survey designs
passive observation
ex post facto design
what are survey used for?
describe
compare
explain
what is a cross sectional study design?
is like taking a snapshot of a group of people or things at one specific point in time. It involves collecting data from a group of participants at a single time point to understand characteristics, behaviors, or conditions.
what is prevalence?
existing cases/ number sampled
what are the strengths of a cross sectional study?
quick
inexpensive
useful for public health planning, evaluating, and monitoring
helps determine association between variable
what are weaknesses of cross sectional studies?
cannot establish cause and effect
temporality
prone to selection bias
rare diseases or rapidly fatal disease = difficult sampling
what is a case control study design?
like detective work to understand the causes of a particular outcome, like a disease. Researchers start by identifying people with the outcome (cases) and people without it (controls). Then they look back in time to compare the two groups, trying to find out what might have caused the outcome.
what are the requirements for the control subjects in a case-control study?
need to be similar on all variables except the exposure and outcome
must be at similar risk of developing the outcome
case and controls must arise from the same population
what are common sources of bias in case-control studies?
recall bias: cases and controls may recall past exposure differently
interviewer/observer bias: the recording of exposure information may vary depending on the investigators knowledge of an individuals disease status
selection bias: controls are unrepresentative of the population that produces the cases
what makes a good case control study?
the right question
clear distinction between cases and controls
sampling frame and strategy
collecting data for cases and controls in the same way
blind the assessor
what are some strengths of case-control studies?
inexpensive
efficient for rare diseases
good to study conditions that would be unethical to expose the participatnts
what are weakness of case-control studies?
finding out past exposures can be difficult
subject to bias
selection of controls can be difficult
what is the odds ratio used to estimate?
the strength of the association between exposure and outcome
what is a cohort study design?
like following a group of people over time to see how their lives unfold. Researchers gather a group of individuals who share a common characteristic or experience Then, they observe and collect data from this group over a period of time, tracking their outcomes and exposures.
is a cohort study prospective or retrospective?
it can be both!
what is the best design for determining the incidence and natural history of a condition?
cohort study
what is prospective cohort study?
A group of people is chosen who do not have the outcome of interest (e.g., stroke).
- The investigator then measures a variety of variables that might be relevant to the development of the condition.
- Over a period of time the people in the sample are observed to see whether they develop the outcome of interest (stroke).
what is a retrospective cohort study?
These use data already collected for other purposes.
- The methodology is the same but the study is performed post-hoc.
- The cohort is “followed up” retrospectively.
- The study period may be many years but the time to complete the study is only as long as it takes to collate and analyze the data.
what are some strengths of a cohort design?
good for studying rare exposures
can establish temporal sequence
can yield incidence (the # of new cases that develop during a specified time)
what are some weaknesses of cohort studies?
loss of some subjects to follow up can affect the outcome
very expensive
source of recall, selection, confounding bias
