You measure 34 textbooks' weights, and find they have a mean
weight of 73 ounces. Assume the population standard deviation is
11.4 ounces. Based on this, construct a 90% confidence interval for
the true population mean textbook weight.
Give your answers as decimals, to two places
Solution :
Given that,
Point estimate = sample mean =
= 73
Population standard deviation =
= 11.4
Sample size = n = 34
Z/2
= 1.645
Margin of error = E = Z/2*
(
/
n)
= 1.645 * (11.4 /
34)
= 3.22
At 90% confidence interval estimate of the population mean is,
- E <
<
+ E
73 - 3.22 <
< 73 + 3.22
69.78 <
< 76.22
(69.78 , 76.22)
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