Study Designs - 1 Flashcards
What 4 characteristics should a good study have?
- scientifically sound
- Valid
- Precise
- Efficient
How do you determine is a study is descriptive or analytical?
Where groups compared?
If yes –> analytical
If no –> descriptive
How do you determine if an analytical study is experimental or observation?
Were study subjects allocated to be treated or exposed?
If yes –> Experimental
If no–> Observational
How do you determine an ecological study from a different observational study?
Were individuals or populations followed in this observational study?
If populations –> Ecological
If individuals –> Other observational study (cross sectional, case control, or cohort)
How do you determine if an observation study is a cross sectional, case control, or cohort study?
What are the individuals choose to represent?
Population –> cross sectional study
Outcome –> Case control study
Exposure –> Cohort study
How do you differentiate a case report from case series or cross sectional study?
How many were involved in the descriptive study?
One –> case report
A few –> case series
Many –> cross sectional (but remember this is NOT comparing groups - descriptive)
What is the difference between a prospective cohort and a retrospective cohort?
The time frame of the study
Retrospective is looking back in time
Prospective is following a group so studying what WILL happen (forward in time)
T/F: Descriptive studies test a hypothesis
FALSE
This does not occur in descriptive studies, but DOES take place in analytical studies
What are some advantages and disadvantages to case reports and case series?
remember these are descriptive
PROS: Require minimal resources, Relatively quick to perform, Provide info to stimulate hypotheses and future analytical studies
CONS: Small sample groups or number of cases so findings may be atypical or aberrant, Findings are not generalizable to the population, strictly descriptive
What descriptive study uses a sample that is meant to represent a population?
Cross sectional
- meant to represent the population - usually population is sampled at one time
- usually the prevalence of a dz is measured
What are some advantages and disadvantages to descriptive cross sectional studies?
PROS: can generalize due to the population (if sampled correctly), fast and cheap, provide a good descriptive baseline for future studies
CONS: Not good for causality (can’t tell if the exposure happened before or after the outcome). Prevalence is of limited value, Diseases of short duration and high mortality will be under represented
What is the purpose of analytical studies?
To determine if there is an association and if so, its strength
***designed to test a hypothesis
**these will ALWAYS compare groups or sub populations
What is an exposure?
Any potential determinant of dz or health status
- an exposure may increase or decrease the amt of dz OR have no effect at all
- once an exposure is shown to be associated with dz, it is a determinant or risk factor
Analytical studies compare groups on the basis of either _______ or _________
Exposure or outcome
Ex: one group that has been exposed vs non exposed cohort (cohort studies)
or one group with dz outcome and one group non diseased controls (case control studies)
Why do we need controls?
Essential for measuring the effect of exposures - they are the reference group
