Critical Value
A critical value is a point on the distribution of the test statistic that separates the rejection region from the non-rejection region. For a given significance level α, the critical value is the value where the tail area(s) equals α. If the test statistic is more extreme than the critical value, H₀ is rejected.
Real World
A sports scientist testing whether a new training programme improves 100 m sprint times uses a one-sided t-test at 5% significance; the critical value from tables determines the threshold the test statistic must exceed.
Exam Focus
When using critical values, explicitly state 'since test statistic > critical value, reject H₀' — do not just quote numbers without a comparison statement.
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