A student is tested to determine whether she can tell butter from margarine. She is blindfolded and given small bites of toast that has been spread with either butter or margarine that have been randomly chosen. The experiment is designed so that she will have exactly 15 bites with butter and 15 bites with margarine. She gets 20 right out of 30 trials. Can she tell butter from margarine at a 0.05 level of significance? Explain.