3. The net weight of packages of beef sold in a supermarket are labeled "3 pounds." A complaint has been made
2. A company wants to estimate the 99% confidence interval for the lifetime of inkjet printer heads produced.
The
1. 225 flight records are randomly selected, giving a sample mean of 11.6 unoccupied seats. Given that the population
Example Class 6
1
THE UNIVERSITY OF HONG KONG
DEPARTMENT OF STATISTICS AND ACTUARIAL SCIENCE
STAT0302 Business Statistics (Semester 2, 2012/2013)
Questions
Confidence Interval
Given
X
∼
N
(
μ,
σ
2
)
, where the population mean
μ
is unknown and the population variance
σ
2
is known. The
(1
−
α
)%
confidence interval estimate for
μ
is given by
¯
x
−
z
α
2
σ
√
n
,
¯
x
+
z
α
2
σ
√
n
where
¯
x
is the sample mean of a sample with size
n
drawn from the population and
P
(
Z > z
α
2
) =
α
2
Determining the sample size
The margin of error is given by half the length of a confidence interval. Suppose we require the margin of error not to be
more than a number
E
at the
(1
−
α
)%
confidence interval, we need a sample of size
n
such that
n
≥
z
α
2
σ
E
2
standard deviation of unoccupied seats in a flight is
σ
= 4.1 seats, estimate a 95% confidence interval for the
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '12
 guo
 Statistics, Normal Distribution, Standard Deviation, Variance, µ, University of Hong Kong

Click to edit the document details