# Sam is the manager of a used clothing store.  He wants to estimate the average amount a customer spends per visit.  A random sample of 70 customers’ receipts gave a mean of = \$7.10 with a standard deviation s = \$2.30.  Find a 99% confidence interval for the average amount spent by all customers. Interpret your findings.

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Sam is the manager of a used clothing store.  He wants to estimate the average amount a customer spends per visit.  A random sample of 70 customers’ receipts gave a mean of = \$7.10 with a standard deviation s = \$2.30.  Find a 99% confidence interval for the average amount spent by all customers. Interpret your findings.

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Step 1

From the provided information,

The population standard deviation is not known therefore t distribution will be used to obtain the confidence interval.

The degree of freedom = n – 1 = 70 – 1 = 69

99% confidence level means α = 1 – 0.99 = 0.01

The critical value of t at 0.01 level of significance with 69 degre...

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