Recently, a friend of yours who works at the local pizzeria stated that she is skeptical of the manager’s claim that they will deliver pizza in 30 minutes or less, anywhere in the local neighborhood. Anxious to put your new hypothesis testing skills to the test, you convince her to request that starting next week, employees record the time of each order and delivery boys record the time of each delivery. Your friend gives you the times. To eliminate the influence of work ethic of some employees (and other factors), you take a random sample of 15 times and find a mean of 31 and a standard deviation of 5. You determine that a 1% significance is adequate in this case.
a) State the null and alternative.
b) Determine the value of t.
c) Calculate the p-value (or a range of values from the t table).
d) Make a decision about the null.
e) Make a statistical conclusion.