Example: 8.2 (Newbold) A process produces bags of rened sugar. The
weights of the contents of these bags are normally distributed with standard
deviation 1.2 ounces. The contents of a random sample of twenty-ve bags had
mean weight 19.8 ounces. Find a 95% condence interval for the true mean
weight for all bags of sugar produced by the process.
Population:
X = "weight of a sugar bag (in oz)"
X N(X ; 2X
= 1:22)
'SRS: n = 25
Sample: x = 19:8
Area=
0.025
l
z0.025 = 1.96
Objective: CI0:95(X ) =
x z=2
pX
n
X = 1:2
n = 25 x = 19:8
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