Study Design (Oh No) Flashcards
Give some study designs
Worst Case report Case series (a collection of case reports) Cross sectional Case control Chief RCT systemic review Best Retrospective generally worst
Describe a cross sectional study
Retrospective observational study where u collect data from a population at one point in time- snapshot
Pros of cross sectional study
Quick
Big sample size
Can repeat over time to see changes
Cons of cross sectional
Issue with reverse causality
Disease length bias (wouldn’t get those who recover quickly)
Sample size too small for rarer outcomes/diseases
What is a case control study
Get a group of people with a condition and some without and ask them about potential exposures. Retrospective
Pros of case control
Good for rare outcomes
Speedy
Cons of case control
Senstive to selection bias
Bad for rare exposure
Hard to find good comparison groups
What is a cohort study
Look at different cohorts with different exposures and see if disease happens
Prospective
Pros of a cohort study
Good for rare exposure
Can establish disease RF- no chance of reverse causality
Can collect data on confounders prospectively
Cons of cohort study
Hard to assess rare disease Drop outs as prospective Large sample size needed Slow Spenny
what is an RCT
Where u get participants and randomly assigned an exposure or control intervention
Like cohort but groups are randomised and double blinded so less risk of selection bias
Pros of RCT
No selection bias/ fewer confounders as prospective and randomised
Compare two groups accurately
Cons of RCT
Ethical issues
Drop outs
Expensive
Time consuming
What is an ecological study
Population based data rather than individual data eg compare two geographical areas or compare two different years
Good for showing large trends
Can be hard to find two groups to compare
