Glossary
dependent variable
The dependent variable is what an experiment measures — the outcome that changes in response to the independent variable.
The dependent variable is what an experiment measures: the outcome that is expected to change when the independent variable changes. In a plate trial where the sanitizer concentration is varied, the dependent variable is the number of colonies counted after incubation.
It is called dependent because its value depends on the independent variable — and, in a well-designed experiment, on nothing else. That is what the constants are for. If one group is incubated for 48 hours and another for 24, the colony count no longer answers the question, because time has been allowed to vary too.
The dependent variable is also the place a hypothesis makes its prediction. If the sanitizer is present, then fewer colonies will grow names the colony count as the measurement that will settle the claim. A stem that asks what was measured, counted or recorded is asking for this variable, and a stem that asks what was changed is asking for the independent one.
Taught in
Related terms
- independent variable — The independent variable is the one condition an experimenter changes on purpose — the input a hypothesis varies to see what follows.
- hypothesis — A hypothesis is a testable, falsifiable statement that predicts what an experiment will show — the proposed answer a controlled test is designed to check.
Source: The biology guide in this course: its genetics definitions follow the National Human Genome Research Institute's Talking Glossary of Genomic and Genetic Terms, and its process descriptions follow the US National Cancer Institute's SEER Training Modules. Both are US federal government material, not subject to copyright in the United States. The microbiology entries — the bacterial cell, the Gram stain and the chain of infection — were written for this course from the infection-control guidance the biology guide's own source list names (US Centers for Disease Control and Prevention), which the genetics glossary does not cover. The definitions above are written for this course in our own words. (NHGRI Talking Glossary accessed 2026-10-26; definitions written 2026-10-27; the CDC basis for the microbiology entries — Principles of Epidemiology in Public Health Practice, third edition — accessed 2026-10-28, the date the biology guide's own source list records)