Scientific method · BEGINNER LESSON
Hypothesis
A hypothesis is a potential explanation for a natural phenomenon. In science, it must be testable, meaning it can generate specific predictions that observations can support or contradict.
What it is
A hypothesis is a proposed explanation for something observed in nature. In science, the word is used for explanations whether they are new or already heavily studied. The key requirement is testability: the idea must lead to predictions about what should be seen if it is true, or what would be unlikely if it is true. A statement that fits every possible observation is not testable and is therefore outside science.
[1] How Science Works - Reference Manual on Scientific Evidence ... [2] Evidence-Based Toxicology—Hypothesis Testing in Randomized ... [3] Table 1.
How scientists use it
Scientists begin with a question and form a research hypothesis, which is a specific prediction tied to a study. In some studies, especially randomized trials, the hypothesis can also be written as a statistical hypothesis with formal numbers or population parameters. Researchers then compare predictions with evidence. Support comes when observations match the predictions; contradiction comes when they do not. Because evidence can be incomplete, scientists also compare alternative hypotheses and look for results that disagree with the idea being tested.
[1] How Science Works - Reference Manual on Scientific Evidence ... [2] Evidence-Based Toxicology—Hypothesis Testing in Randomized ...
What makes testing stronger
Scientific testing is stronger when results can be replicated, meaning similar studies in similar settings give concordant results. Scientists also try to use more than one method, a process called triangulation, because a single study can miss biases or oversights. When statistics are used, a common threshold is 0.05, which means the null hypothesis would produce results as extreme as the observed data only about 5% of the time. The null hypothesis is the claim that there is no difference between groups, and the alternative hypothesis is the test’s competing claim.
[1] How Science Works - Reference Manual on Scientific Evidence ... [2] Evidence-Based Toxicology—Hypothesis Testing in Randomized ...
Limits and common confusion
Science does not prove or disprove hypotheses in an absolute sense. A hypothesis can be supported or contradicted by evidence, but later studies may change how well it fits the data. Also, the words hypothesis, theory, and law are all scientific explanations, but they differ in breadth rather than in level of support. In ordinary language, people may use hypothesis more loosely, but in science it has the special meaning of a testable explanation.
[1] How Science Works - Reference Manual on Scientific Evidence ... [2] Evidence-Based Toxicology—Hypothesis Testing in Randomized ... [3] Table 1.
SEE THE IDEA
How a hypothesis is tested
A natural pattern or problem is noticed.
A testable explanation is proposed.
The hypothesis generates expected observations.
Measurements are compared with the prediction.
The idea is supported, contradicted, or revised.
Observation leads to a testable explanation, which leads to predictions that are checked against evidence.
A hypothesis is useful in science only when it can produce predictions that observations can confirm or contradict.
TRY IT YOURSELF
Test your understanding
Choose an answer, then check the explanation.
PUT IT TOGETHER
Match each concept to its meaning
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4 pairs to match
Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.