When these steps are followed,two types of error can occur,as shown in Table 2.5. If is hoped that the correct decision concerning the null hypothesis will be reached after examining sample evidence,but there is always a possibility of rejecting a true H0 and
Failing to reject a false H0. The probabilities of these events are known as alpha(แอลฟา) and beta(เบต้า) ,respectively.Alpha is also Known as the significance level of test.