#23 this is my timed final please help

23. The faculty at a large university is irritated by students' cell phones. They have been complaining for the past few years that a cell phone rings in class at least 15 times a semester (which is about once a week.) A reporter for the school newspaper claims that students are more courteous with their cell phones now than in semesters past, and the average is now lower than 15. The reporter asks select teachers to keep track of the number of times a cell phone rings in each of 12 different classes in one semester. The sample mean is 14.8 with a standard deviation of 1.2 calls. Does the evidence support the claim at the 0.10 level of significance? Include all steps of the hypothesis test