Using a confidence interval to decide whether to reject the null hypothesis

Suppose that you do a hypothesis test. Remember that the decision to reject the null hypothesis (H₀) or fail to reject it can be based on the p-value and your chosen significance level (also called α). If the p-value is less than or equal to α, you reject H₀; if it is greater than α, you fail to reject H₀.

Your decision can also be based on the confidence interval (or bound) calculated using the same α. For example, the decision for a test at the 0.05 level of significance can be based on the 95% confidence interval:

If the reference value specified in H₀ lies outside the interval (that is, is less than the lower bound or greater than the upper bound), you can reject H₀.
If the reference value specified in H₀ lies within the interval (that is, is not less than the lower bound or greater than the upper bound), you fail to reject H₀.