Alpha, Significance Level of Test

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 ...