SOLUTION: A random sample of 99 customers, who visited a department store, spent an average of $80 at this store. Suppose the standard deviation of expenditures at this store is σ= $20.
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Question 1054066: A random sample of 99 customers, who visited a department store, spent an average of $80 at this store. Suppose the standard deviation of expenditures at this store is σ= $20. The 98% confidence interval for the population mean (rounded to two decimal places) is:
The lower limit is $
You can put this solution on YOUR website! 98% confidence interval
x̄ =80, n = 99 and σ= 20
ME = ± , z = invNorm(.99) = 2.326
ME = ±
confidence interval for the population mean ( (rounded to two decimal places)
80- ME < < 80 + ME
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= CI z = value
90% z =1.645
92% z = 1.751
95% z = 1.96
98% z = 2.326
99% z = 2.576
