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Section 9.6 Glossary

hypothesis testing
A set of methods for checking whether an observed effect could plausibly be due to random sampling.
test statistic
A statistic used in a hypothesis test to quantify the size of an observed effect.
null hypothesis
A model of a system based on the assumption that an effect observed in a sample does not exist in the population.
permutation
A way to simulate a null hypothesis by randomly shuffling a dataset.
p-value
The probability of an effect as big as the observed effect, under a null hypothesis.
statistically significant
An effect is statistically significant if the p-value is smaller than a chosen threshold, often 5%. In a large dataset, an observed effect can be statistically significant even if it is too small to matter in practice.