b3-length-biased-prevalence {ctfepi}sealed case file
Length-Biased Prevalence
Case B3, The Map in the PaperCross-Sectional and Ecological Studiesscene 4hard400 pts
Case
A newspaper map links district salt sales to stroke; you test what district data can and cannot say.
What this scene will ask
Prevalent cases overrepresent long durations.
Planned flag: mean duration among prevalent cases, 2 dp; mean duration among incident cases, 2 dp; their ratio*, 3 dp.
Status
[#] Sealed. This scene opens when it is written and passes review. Nothing on CTFEpi expires, so there is no rush.