I am looking for information for some extended family members.
A medical procedure has a $4$% chance of stroke per year over $5$ years. One family member has said that that is a $20$% chance of stroke over all ($5\times 4$%). Others argue that it is less because $4$% each year is smaller. I am not sure how to frame this question in order to get an accurate answer. Is the chance of something happening being $4$% a year for $5$ years the same as say an instantaneous $20$% chance of something happening?