Study terminology guides

Common Study Terms

Vocabulary grouped by study type, plus one good question to ask for each.

General Clinical Research

The core vocabulary that appears in almost every study description.

Protocol: The detailed written plan for a study: its purpose, who can join, what happens at each visit, and how results are measured.
Informed consent: The ongoing process of learning about a study, asking questions, and freely deciding whether to take part. You can change your mind at any time.
Eligibility criteria: The list of requirements a study uses to decide who can and cannot take part. Each study sets its own list.
Endpoint: The specific result a study measures to answer its main question.
Adverse event: Any unwanted health change that happens to a volunteer during a study, whether or not it is caused by the thing being studied.

A question to ask a study team: What happens at each visit, and how long does the whole study last?

Words that describe how volunteers are fairly assigned to groups.

Randomization: Assigning volunteers to groups by chance, like a coin flip, so the groups are fair to compare.
Arm: A group of volunteers in a study who all follow the same plan.
Control group: The group that does not receive the approach being tested, used as a point of comparison.
Crossover design: A setup where each volunteer tries more than one approach, one after another, in a planned order.

A question to ask a study team: How many groups are there, and what is my chance of being in each?

Terms for studies that compare an approach with an inactive look-alike.

Placebo: An inactive look-alike, such as a sugar pill, used so researchers can compare it with the approach being tested.
Placebo effect: A real change people notice simply because they expect something to help.
Blinding: Keeping certain people from knowing which group a volunteer is in, so expectations do not shape the results.
Washout period: A break between parts of a study so the effects of one approach fade before the next begins.

A question to ask a study team: Is a placebo used, and will I learn which group I was in afterward?

Language for studies that watch and record rather than assign.

Observational study: A study where researchers watch and record what happens without assigning volunteers to a specific approach.
Cohort: A group of people who share something in common and are followed over time.
Longitudinal study: A study that collects information from the same people repeatedly over a long period.
Retrospective study: A study that looks back at information that was already collected in the past.

A question to ask a study team: What information is collected, and how often will I be contacted?

Vocabulary for the first, smallest stages of testing.

Phase: A stage of testing. Earlier phases focus on safety in small groups, while later phases involve more people and compare results.
First-in-human study: The first time a new approach is tried in people, usually with a very small group and close monitoring.
Healthy volunteer: A person without the condition being studied who takes part to help researchers learn about safety or how the body responds.
Dose escalation: Slowly increasing the amount of something being studied across small groups to learn how much is well tolerated.

A question to ask a study team: How closely will I be monitored, and who can I contact with concerns?