Example 1: Filling Machine
A machine is used to fill liquid (milk or soft drink) into
1-liter (or 1,000 cc) containers. Ideally, the amount of
liquid filled should vary only slightly. The manager of
this operation would like to estimate the variance of
the amount of liquid filled in a container.
Suppose a sample of 25 containers is taken. For this
sample, it is found that s
2 = 0.8088 cc.
Analysis: The point estimate for σ
2
is simply 0.8088.
The 95% confidence interval for σ
2
is given by (6)
with n = 25 and α = 0.05. That is,