In a large lecture class, a professor decides to make his class notes available on the Internet. During one of his lectures, he mentions that he would like some feedback concerning the usefulness of these notes. He asks students to leave written comments in his mailbox regarding the usefulness of having the class notes available on the Internet. He gets written comments from twenty-three students, and, in their written comments, most indicate that having the notes readily available helped them in the course. This is an example of