AtlasSession 3L8: Study designp.9–19, 92–97
Cross-sectional studies
- Study designs primer
- Classification
- Cross-sectional studies
Fig. 1
Pressure ulcers in 4,000 surgical inpatients on one day (patients with an ulcer)
Fig. 1: a photo of the ward on one day. A scanner sweeps the 4,000 surgical inpatients and lights those with a pressure ulcer: 540, which is 13.5 in every 100. One photo can’t show whether immobility or the pressure ulcer came first.
- With a pressure ulcer today
- 540 of 4,000
- In every 100 patients
- 13.5
- Which came first?
- can’t tell from one photo
Study Timeline · First look
Level 1 · First look · Lecture 8 · p.9–19, 92–97
Understand a one-day snapshot and the share of people who have something.
Compute prevalence = r/n, name point, period and lifetime prevalence, and explain why a snapshot cannot show which came first.
Class photo (the step you are on)
One picture shows who wears glasses today, not who will need them next year.
One class photo shows who wears glasses today, not who will need them next year. One photo of the ward: 540 of 4,000 patients have a pressure ulcer today.