"Alpha and beta also refer to the probabilities of making particular errors based on whether the null hypothesis (H0) is or is not rejected. Recall that the null hypothesis is that there is no difference between groups in a clinical trial and that the analysis of trial results involves deciding whether or not H0 is plausible. The procedure used to determine the plausibility of H0 is called hypothesis testing. A p-value is calculated assuming that H0 is true and tells us the probability of observing results at least as different as our expectation under H0 of no difference between the groups. The p-value is compared to α, the pre-determined level at which we reject the null hypothesis. Most commonly, α is set at 0.05: if the p-value is 0.05, we conclude that there is insufficient evidence to reject H0. By setting α at 0.05, the probability of making an alpha error or false positive due to a random error is 0.05."
"Clinical trials may have incorrect results due to random error or bias. The two types of random error are called alpha (α) and beta (β), also known as type I and type II errors, respectively. Alpha and beta errors are both conditional probabilities. For Radiologists, it may be helpful to think of α or type I error as a false positive (FP) and β or type II error as a false negative (FN)."