Encyclopedia Entry

Alpha, Significance Level of Test

Andrew Noymer

Alpha is a threshold value used to judge whether a test statistic is statistically significant. It is chosen by the researcher. Alpha represents an acceptable probability of a Type I error in a statistical test. Because alpha corresponds to a probability, it can range from 0 to 1. In practice, 0.01, 0.05, and 0.1 are the most commonly used values for alpha, representing a 1%, 5%, and 10% chance of a Type I error occurring (i.e. rejecting the null hypothesis when it is in fact correct). If the p-vahie of a test is equal to or less than the chosen level of alpha, it is deemed statistically significant; otherwise it is not. The typical level of alpha is 0.05, but this is simply a custom and is not based on any statistical science theory or criteria other than conventional practice that has become the accepted standard. Alpha levels of 0.1 ...

Users without a subscription are not able to see the full content on this page. Please, subscribe or login to access all Methods content.

Click here to see full text

Articles in Google Scholar by