Testing ways to diagnose a disease early, sometimes before there are symptoms.Often, a clinical trial is designed to learn if a new treatment is more effective or has less harmful side effects than existing treatments. These trials are the primary way that researchers determine if a new form of treatment or prevention, such as a new drug, diet, or medical device (for example, a pacemaker), is safe and effective in people. Observational studies do not test a medical intervention, such as a drug or device, but may help identify new treatments or prevention strategies to test in clinical trials.Ĭlinical trials are research studies that test a medical, surgical, or behavioral intervention in people. For example, researchers may ask a group of older adults about their exercise habits and provide monthly memory tests for a year to learn how physical activity is associated with cognitive health. Researchers gather information from people and compare changes over time. Observational studies monitor people in normal settings. Read and share this infographic (PDF, 317K) to learn why researchers do different kinds of clinical studies.