Lexie is a waitress. She believes that she earns more tips, on average, when she curls her hair before work rather than pulling it back in a ponytail. In order to investigate this belief, she writes “curls” on 30 slips of paper and “ponytail” on 30 slips of paper, puts them in a hat and mixes them well. Each time she gets ready for work she randomly selects one piece of paper to determine how she should do her hair that day. Using the data she collects, she carries out a t test for a difference in means in order to test these hypotheses: