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

In a study of human cognition, we want to look at recall of four different classes of words (nouns, verbs, adjectives, and adverbs). Each subject will see one of each. We are afraid that the order of presentation of the words may affect the results, so we want each participant to have a different order. How many participants will we need to have one participant per order?