A valid investigation actually tests the hypothesis and answers the question. That needs a fair test, a suitable range of the independent variable, enough intervals within it (usually at least five), and repeats. Where results change quickly, extra readings in that region improve the pattern.
In biology, living things vary, so large samples and control groups are needed; a control group experiences everything except the factor being tested. In chemistry and physics, controlling temperature and using precise instruments are often key. Peer review lets other scientists check the method and conclusions before results are accepted.
Worked example
Why does a drug trial need a control group given a placebo?
- People may feel better just because they expect to.
- The control group shows this placebo effect.
Answer:Comparing groups shows the drug's real effect.
Key words
- valid
- the method tests what it claims to test
- interval
- the gap between values of the independent variable
- placebo
- a dummy treatment
- peer review
- checking by other experts
New questions every time.
NGSS-referenced: HS-ETS1-3