state the distribution to use for the test. (enter your answer in the form of z or tdf where df is the degrees of freedom. round your answer to three decimal places.)

7. [13/14 Points] DETAILS PREVIOUS ANSWERS ILLOWSKYINTROSTAT1 10.1.082.HW.ALT. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Marketing companies have collected data implying that teenage girls use more ring tones on their cellular phones than teenage boys do. In one particular study of 40 randomly chosen teenage girls and boys (20 of each) with cellular phones, the mean number of ring tones for the girls was 3.3 with a standard deviation of 1.6. The mean for the boys was 1.8 with a standard deviation of 0.7. Conduct a hypothesis test at the 5% level to determine if the means are approximately the same or if the girls' mean is higher than the boys' mean. NOTE: If you are using a Student's t-distribution for the problem, including for paired data, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.) Part (a)