In an increasingly data-driven world, it is more important than ever for students as well as professionals to better understand basic statistical concepts. 100 Questions (and Answers) About Statistics addresses the essential questions that students ask about statistics in a concise and accessible way. It is perfect for instructors, students, and practitioners as a supplement to more comprehensive materials, or as a desk reference with quick answers to the most frequently asked questions.

# What Is a Null Hypothesis, and How Is It Used?

### What Is a Null Hypothesis, and How Is It Used?

The null hypothesis (null meaning “none” or “void”) is a statement of equality. It is the conceptual starting point that reflects no relationship exists between variables. Why? Because given no other knowledge of the relationship between variables, the null hypothesis is the only logical place to begin a research effort.

A null hypothesis can take this form:

${\text{H}}_{0}:{\phantom{\rule{0.5em}{0ex}}µ}_{1}={\phantom{\rule{0.5em}{0ex}}µ}_{2},$

where

• H0 equals the research hypothesis,
• µ1 equals the value of the population parameter for group 1, and
• µ2 equals the population parameter for group 2.

Note that the above example, that the null hypothesis is that two group averages are equal, is only one of many examples of the null.

For example, the following null hypothesis assumes no relationship between participation in a ...