The fundamental difference between a null hypothesis (H₀) and an alternative hypothesis (H₁) is their claim about the population. The null hypothesis represents the assumption of no effect, no difference, or no relationship—it is the default statement we try to test against. In contrast, the alternative hypothesis suggests that there is an effect, a difference, or a relationship—it represents what the researcher is trying to prove. Simply put, H₀ assumes nothing has changed, while H₁ assumes that something has changed.