Aresearcher is interested in the cholesterol levels of adults in the city in which she lives. a free cholesterol screening program is set up in the downtown area during the lunch hour. individuals can walk in and have their cholesterol levels determined for free. one hundred and seventy three people us the service, and their average cholesterol is 217.8. the sample obtained is an example ofa. a simple random sample, since the experimenter did not know beforehand which individuals would come to the screening. b. a stratified sample of high and low cholesterol individuals. c. a sample probably containing bias and undercoverage. d. a multistage sample of varying cholesterol levels.