What does a level of significance of .05 mean?

A level of significance of 0.05 indicates that there is a 5% risk of rejecting the null hypothesis when it is actually true, commonly referred to as a Type I error. In hypothesis testing, it establishes a threshold for determining whether the observed data is statistically significant. If the p-value obtained from the test is less than or equal to 0.05, the null hypothesis is typically rejected in favor of the alternative hypothesis. This level is widely used in scientific research to balance the risk of errors with the need for robust conclusions.