Null Hypothesis
The null hypothesis H₀ is a statement that specifies no change, no effect, or no difference between groups. It represents the 'status quo' or baseline assumption. The alternative hypothesis H₁ represents the claim being investigated. The hypothesis test evaluates whether sample data provides sufficient evidence to reject H₀ in favour of H₁.
Real World
When the Food Standards Agency tests whether mercury levels in supermarket tuna exceed safe limits, H₀ states that the mean mercury level equals the safety threshold — the 'innocent until proven guilty' baseline.
Exam Focus
Always write H₀ as an equality (e.g. μ = k) and H₁ as the appropriate inequality matching the context.
How well did you know this?