An alpha level of 0.05 means what? What about an alpha level of 0.01, 0.001, 0.10, and 0.20?

Question

An alpha level of 0.05 means what?  What about an alpha level of 0.01, 0.001, 0.10, and 0.20?

Answer 1

Those are essentially the chances of making a type I error in rejecting the null hypothesis.  So, 0.05 is equivalent to a 5% chance; 0.01 is a 1% chance; 0.001 is a 0.1% chance, etc.  Put another way, it represents the chance of incorrectly rejecting a true null hypothesis.