The researchers divide the heart attack patients based on race, and then measure the cholesterol levels of randomly selected patients in each race
grouping.

The researchers list all of the heart attack patients and measure the cholesterol level of every 25th person on the list.

The researchers go to one hospital on a given day and measure the cholesterol level of the heart attack patients at that time.

The researchers randomly select 5 hospitals in the U. S. then measure the cholesterol
levels of all the heart attack patients in each of those hospitals.

The researchers list all of the heart attack patients. They then measure the cholesterol
levels of randomly selected patients.

a. convenience sample
b. simple random sample
c. stratified sample
d. systematic sample
e. cluster sample