Final answer:
The study in question is a retrospective study, where researchers look back in time to analyze data from subjects to determine a correlation between aspirin use and heart disease.
Step-by-step explanation:
The research study described involves selecting samples of subjects with and without heart disease and then looking back in time to determine their aspirin use.
This type of study is known as a retrospective study, which is an observational study where researchers collect data from past records and analyze them to identify correlations or patterns.
Retrospective studies differ from cross-sectional studies, which involve analyzing different segments of the population at the same point in time, and prospective studies, which track subjects over a period going forward from the start of the study.