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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 H0:μ=45 minutes versus Ha:μ45 minutes, where μ 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 t2.37 and a P-value of approximately 0.023. Assume that the conditions for inference were met.
Is there sufficient evidence at the α=0.05 level to conclude that the mean delivery time has changed from 45 minutes?
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