Hypothesis Testing
Middle School
Definition
Using experiments and evidence to support or reject a hypothesis, a proposed explanation for an observation. A fair test is designed to see whether the predicted outcome actually occurs, helping decide if the idea is well supported.
Worked examples
Hypothesis: Plants grow faster with more sunlight. Test: Grow identical plants with different light amounts, measure growth after two weeks.
A fair test keeps everything the same except light, so any growth difference supports or rejects the hypothesis.
Hypothesis: Salt lowers water's freezing point. Test: Freeze pure water and salt water at the same time, record which freezes first.
The evidence from timing shows whether the prediction matches reality, testing the explanation.
Common mistakes
- changing multiple variables at once (light and water amount) → change only one variable (light) and keep all others constant If you change two things, you cannot tell which one caused the result — the test is not fair.
- accepting the hypothesis after one trial that supports it → repeat the test multiple times and look for consistent evidence One trial might be a fluke; reliable science requires repeated tests and consistent results.
- ignoring data that contradicts your hypothesis → use all the evidence to decide whether to support or reject the hypothesis Cherry-picking data leads to wrong conclusions; honest testing uses every result.
Where you'll use it next
You'll use hypothesis testing throughout science courses to design experiments in biology, chemistry, and physics, and in real research to solve problems and discover new knowledge.
See also
Investigation DesignData CollectionData AnalysisDrawing ConclusionsScientific TheoryVariable Control
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026