You measure 29 textbooks' weights, and find they have a mean
weight of 78 ounces. Assume the population standard deviation is
13.2 ounces. Based on this, construct a 95% confidence interval for
the true population mean textbook weight. Round answers to at least
4 decimal places.
= Solution :
Given that,
Point estimate = sample mean =
= 78
Population standard deviation =
= 13.2
Sample size n =29
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.96 ( Using z table )
Margin of error = E = Z/2
* (
/n)
=1.96 * ( 13.2/
29)
= 4.8043
At 95% confidence interval estimate of the population mean
is,
-+ E
78+-4.8043
(73.1957 ,82.8043)
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