Suppose you are testing someone to see whether he or she can tell butter from margarine when it is spread on toast. you use many bite-sized pieces selected randomly, half from buttered toast and half from toast with margarine. the taster is blindfolded. the null hypothesis is that the taster is just guessing and should get about half right. when you reject the null hypothesis when it is actually true, that is often called the first kind of error. the second kind of error is when the null is false and you fail to reject. report the first kind of error and the second kind of error.