A nutritionist follows 500 adults for 10 years, recording their self-reported coffee consumption and tracking heart-disease incidence. She does not assign any participant to drink or avoid coffee.
This study is best described as
- A
A matched-pairs experiment
- Bcheck_circle
An observational study
- C
A randomized experiment
- D
A blocked experiment
Explanation
No treatment is imposed by the researcher; she merely observes existing coffee habits and outcomes. This is an observational study.