Final answer:
A cross-sectional study is an observational study that collects data from a sample of subjects at one point in time. It is often used to find variables that may be linked and further investigate the relationship between them.
Step-by-step explanation:
A cross-sectional study is a type of observational study that collects data from a sample of subjects just once at a certain point in time. Cross-sectional studies are often used to find variables that may be linked and then further investigated using a case-control or cohort study to establish a possible relationship between the variables.