What Is a Two Tailed Hypothesis?

A two-tailed hypothesis test is designed to show whether the sample mean is significantly greater than and significantly less than the mean of a population. The two-tailed test gets its name from testing the area under both tails (sides) of a normal distribution.

How do you write a two tailed hypothesis?

Hypothesis Testing — 2-tailed test
  1. Specify the Null(H0) and Alternate(H1) hypothesis.
  2. Choose the level of Significance(α)
  3. Find Critical Values.
  4. Find the test statistic.
  5. Draw your conclusion.

What is the difference between one and two tailed?

A one-tailed test has the entire 5% of the alpha level in one tail (in either the left, or the right tail). A two-tailed test splits your alpha level in half (as in the image to the left). Let's say you're working with the standard alpha level of 0.5 (5%). A two tailed test will have half of this (2.5%) in each tail.

Sarah Jenkins

Sarah Jenkins

Senior Technology Editor & AI Specialist

Sarah Jenkins is a veteran tech journalist with over 12 years of experience covering artificial intelligence, mobile innovations, and digital ethics. Her insights have appeared in leading technology publications worldwide.