 In research, while studying relationship or association between two variables, we make two hypotheses, that is, null hypothesis and research or alternate hypothesis. Null hypothesis says there is no relationship whereas your alternate hypothesis says there is a relationship. In reality, there may be two possibilities that null hypothesis may be true or false. On the other hand, in your study, you may either accept it or reject it. If you rightly accept the true null hypothesis and reject the null hypothesis when it is false, those two are right decisions. On the other hand, if you reject the null hypothesis when it is actually true, that is called as type 1 error or alpha error. When you accept the null hypothesis, when it is actually false, that is called as beta error. Now, how to remember this? You can remember by ART. A stands for alpha error, rejecting null hypothesis when it is actually true. The reverse of this, that is beta error, is accepting the null hypothesis when it is actually false. So, you have to remember ART. The probability of committing alpha error is called as the p value. The inverse of beta is called as power of the study.