Claim: stents are as effective as surgery, not different from surgery (in terms of setbacks). Claim is about stents.

From surgery (Comparison Criteria) 38.6% suffered a setback (heart attack, stroke, or death)

Sample - Data to be tested (from stents treatment) n=143 patients x=41 suffered a setback

You want to test and see if the proportion of those that had a setback is not different for stents as it is for surgery.