A hypothesis describing no difference between groups on a variable is called

• A. Alternative
• B. Confounding
• C. Modifying
• D. Null

Answer: (D)

In hypothesis testing, the statement that there is no difference between groups on the variable of interest is the null hypothesis. It sets the default assumption that any observed difference is due to random variation rather than a real effect. The alternative hypothesis is the claim that a true difference exists. For example, when comparing means between two groups, the null posits equal means, and the test assesses whether the data provide enough evidence to reject that claim. The other terms describe different ideas: a confounding variable is an extraneous factor that can distort the observed association, and effect modification (modifying) is when the effect differs across levels of another variable.