The amount of time customers at the “Speedy” tyre store spend waiting for their car tyres to be checked has a (unknown) mean $\mu$ \mu and standard deviation $\sigma$ \sigma = 4 minutes. It is company policy that the customer wait time should be 20 minutes (or less). The manager of the store selects a random sample of 150 customer wait times and observes a mean wait time of 21 minutes.
A 99% confidence interval for the population mean wait time based on this sample was calculated to be (20.16, 21.84) minutes.
Which of the following statements is true?

Question

The amount of time customers at the “Speedy” tyre store spend waiting for their car tyres to be checked has a (unknown) mean $\mu$ \mu and standard deviation $\sigma$ \sigma = 4 minutes. It is company policy that the customer wait time should be 20 minutes (or less). The manager of the store selects a random sample of 150 customer wait times and observes a mean wait time of 21 minutes.

A 99% confidence interval for the population mean wait time based on this sample was calculated to be (20.16, 21.84) minutes.

Which of the following statements is true?

Answer

The 99% confidence interval obtained from this sample is unreliable because the population distribution is not Normal.

Answer

The 99% confidence interval obtained from this sample is untrustworthy because the sample is biased.

Answer

We can conclude with 99% confidence that the mean waiting time for all customers of the “speedy” tyre store is estimated to be between 20.16 minutes and 21.84 minutes.

Answer

The company is underperforming in their customer services because they failed to meet their company policy of no more than 20 minutes waiting time.

Crowdly

The amount of time customers at the “Speedy” tyre store spend waiting for their...

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