The scientific method as a cycle
Observation → hypothesis → prediction → test → analyse → evaluate, then round again.
Science is not a single experiment — it is a repeating cycle in which observations and ideas constantly test each other.
The stages:
- Observation — you notice something (e.g. fewer fish in a river downstream of a factory).
- Hypothesis — you propose a testable explanation (e.g. the factory's waste lowers oxygen levels, reducing fish numbers).
- Prediction — you state what you would expect to find if the hypothesis is true (e.g. dissolved oxygen will be lower downstream than upstream).
- Test (investigation) — you collect quantitative data under controlled conditions.
- Analyse — you process the data (tables, graphs, calculations) and compare with your prediction.
- Evaluate — do the data support or refute the hypothesis? You judge the quality of your evidence and identify limitations.
- Repeat / refine — you modify the hypothesis or design a better test, and go round again.
Hypothesis vs theory. A hypothesis is a single testable idea. When a hypothesis is tested many times by different scientists and consistently supported by the evidence, it can become a theory — a well-established, widely-accepted explanation (for example, the theory that human greenhouse-gas emissions are warming the climate). A theory is not "just a guess": in science it is the strongest kind of explanation.
- The method is a repeating cycle, not a one-off experiment.
- Observation → hypothesis → prediction → test → analyse → evaluate → refine.
- A hypothesis is a testable statement.
- A hypothesis supported repeatedly by evidence can become a theory.
- In science a 'theory' is a strong, well-tested explanation — not a guess.