Hyp testing #3: Testing for μ when σ is unknown

Example question: An online fashion store called Showdonkey advertises that its average delivery time is less than six hours for local deliveries. A random sample of the amount of time taken to deliver packages to an address in Stanmore produced the following delivery times (rounded to the nearest hour): 7 3 4 6 10 5 6 4 3 8 Is there sufficient evidence to support Showdonkey's advertisement, at the 5% level of significance? VIDEO LINKS TO COME!