Chapter 8: Confidence Intervals
for One Population Mean
8.1
Estimating a Population Mean
Vocab
• Point Estimate
– The value of a statistic used to estimate a parameter
• Confidence-interval estimate
– Consists of an interval of numbers obtained from a point
estimate of the parameter and a percentage that
specifies how confident we are that the parameter lies in
the interval
– The confidence percentage is called the confidence level
Example 8.2
• From a Census Bureau survey, the prices of new
mobile homes is normally distributed, with a
sample mean of $42,280. The standard deviation of
such prices is $7200.
• A. Identify the sampling distribution of the sample
mean for samples of size 36.
Example 8.2
• From a Census Bureau survey, the prices of new
mobile homes is normally distributed, with a
sample mean of $42,280. The standard deviation of
such prices is $7200.
• B. Show that 95.44% of all samples of 36 new
mobile homes have the property that the interval
from xbar ± 2.4 contains μ
Example 8.2
• From a Census Bureau survey, the prices of new
mobile homes is normally distributed, with a
sample mean of $42,280. The standard deviation of
such prices is $7200.
• C. Use part (b) and the sample data in table 8.1 to
obtain a 95.44% confidence interval for the mean
price of all new mobile homes.
Homework
• P. 346
• 1–8