A/B tests

Question 1

What is type I error? How is it also called?

Answer 1

Probability of rejecting H0 when it’s true.(wrongly detecting an effect). It’s also called significance (alpha)

Question 2

What is type II error? How is it also called?

Answer 2

Probability of accepting H0 when it’s actually false (missing an effect). It’s used in what is also called the power of a test (1-beta).