Null and Alternative Hypotheses · Exercise 14

Previously, an organization reported that teenagers spent 4.5 hours per week, on average, on the phone. The organization thinks that, currently, the mean is higher. Fifteen randomly chosen teenagers were asked how many hours per week they spend on the phone. The sample mean was 4.75 hours with a sample standard deviation of 2.0. Conduct a hypothesis test. The null and alternative hypotheses are:

(a) H_o: $\bar{x}$ = 4.5, H_a: $\bar{x}$ > 4.5
(b) H_o: μ ≥ 4.5, H_a: μ < 4.5
(c) H_o: μ = 4.75, H_a: μ > 4.75
(d) H_o: μ = 4.5, H_a: μ > 4.5

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Introductory Statistics 2e · §9.1 Null and Alternative Hypotheses · Exercise 14