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### Kurs: Statystyka - program rozszerzony>Rozdział 11

Lekcja 4: Testowanie hipotez o średniej

# Wyciąganie wniosków z testu t dla średniej

A local pizza store knows the mean amount of time it takes them to deliver an order is $45$ minutes after the order is placed. The manager came up with a new system for processing delivery orders, and they were curious if it changed the mean delivery time. They took a sample of $40$ delivery orders to test ${H}_{0}:\mu =45$ minutes versus ${H}_{\text{a}}:\mu \ne 45$ minutes, where $\mu$ is the mean delivery time under the new system.
The delivery times in the sample had a mean of $48$ minutes and a standard deviation of $8$ minutes. These results produced a test statistic of $t\approx 2.37$ and a P-value of approximately $0.023$. Assume that the conditions for inference were met.
Is there sufficient evidence at the $\alpha =0.05$ level to conclude that the mean delivery time has changed from $45$ minutes?