An epidemiologist wishes to study the factors which might contribute to heart disease. They ask doctors to provide biometric data on patients recently diagnosed with heart disease as well as data on patients who have not been diagnosed with heart disease. Is this an example of an observational study or an experiment? What are some possible sources of error? State at least two.

step-by-step explanation:

i dont get

if you are saying purchasing 3 social media ads and one newspaper ad counts as one purchase then there are:

6 purchases

if you are asking how many of each then:

18 social media ads

6 newspaper ads

you have to wait a while to reward brainliest if only one person answers. if 2 people answer there should be a "mark brainliest" on their question.

i cant fully remember all of the ranks, here are the ones i remember.

hand, ambitous, ace, genius.