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The data below gives the mean price (in cents) of a litre of regular gasoline at self-service filling stations at a sample of six urban centres in Canada in May .

$\begin{array}{c|c} \text{Urban area} & \text{Price/litre} \\ \hline \text{} & \\ \text{} & \\ \text{} & \\ \text{} & \\ \text{} & \\ \text{} & \end{array}$

Provide answers to the following to two decimal places.

Part (a) Find the sample mean (in cents).

Part (b) Find the sample standard deviation (in cents).

Part (c) Using the appropriate t distribution, find a 90% confidence interval for the mean gasoline price per litre across urban Canada in May . Provide the upper and lower bounds for your confidence interval. ( , )

Part (d) Would a 95% confidence interval be wider or narrower than the interval you found in Part (c)? Using the appropriate t distribution, find a 95% confidence interval for the mean gasoline price per litre across urban Canada in May . Provide the upper and lower bounds for your confidence interval. ( , )

You can earn partial credit on this problem.