In a study of human cognition, we want to look at recall of different classes of words (nouns, verbs, adjectives, and adverbs). Each subject will see one of each. We are afraid that there may be a...

In a study of human cognition, we want to look at recall of different classes of words (nouns, verbs, adjectives, and adverbs). Each subject will see one of each. We are afraid that there may be a sequence effect, however, and want to have different subjects see the different classes in a different order. How many subjects will we need if we are to have one subject per order?