Solution :
Given that,
Point estimate = sample mean =
= $12.16
Population standard deviation =
= $1.87
Sample size = n =44
At 99% confidence level the z is ,
= 1 - 99% = 1 - 0.99 = 0.01
/ 2 = 0.01 / 2 = 0.005
Z_{/2} = Z_{0.005} = 2.576
Margin of error = E = Z_{/2}* ( /n)
= 2.576 * ( 1.87/ 44)
= 0.7
At 99% confidence interval estimate of the population mean is,
- E < < + E
12.16 - 0.7 < <12.16 + 0.7
11.5< < 13.2
(lower limit $11.5 , upper limit$13.2)
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