Final answer:
An observational study measures characteristics in a sample without manipulating variables of interest, while an experiment applies a treatment to compare groups.
Step-by-step explanation:
An observational study is when the researcher measures characteristics in a sample but does not manipulate variables of interest.
A simple example of an observational study is a political poll, where a sample of adults is asked about their age and candidate preference.
In contrast, an experiment is when the researcher applies a treatment to a group and compares it to a control group to isolate the effects of the treatment on an outcome variable.
For example, a study investigating the effects of aspirin on reducing the risk of a heart attack would be an experiment if participants are randomly assigned to take aspirin or a placebo.