1. A cohort study is conducted to assess the association between clinical characteristics and the risk of stroke. The study involves n = 1250 participants who are free of stroke at the study start. Each participant is assessed at study start (baseline) and every year thereafter for 5 years. The following table displays data on hypertension status measured at baseline and hypertension status measured 2 years later.

\f2 Yea rs Later: Not Hypertensive 2 Years Later: Hypertensive Baseline: Not Hypertensive 850 148 Baseline: Hypertensive 45 207 Free of Stroke at 5 Years Stroke Baseline: Not Hypertensive 952 46 Baseline: Hypertensive 234 18 Group Number Randomized Number Free of Hypertension at 12 Weeks Placebo 50 6 New Drug 50| 14