Download IV. B. Confidence Intervals

Example
In a simple random sample of 150 households, the
sample mean number of computers was 1.32. Assume a
population standard deviation of 0.41.
 What is the Z for a 95% confidence interval?
 Construct and interpret a 95% confidence interval for
the population mean number of personal computers
per household.
We are 95% confident that the population mean number
of personal computers per household is between 1.254
and 1.386.
Example
In a simple random sample of 150 households, the
sample mean number of computers was 1.32. Assume a
population standard deviation of 0.41.
 How would the confidence interval change if you were
to change the confidence level from 95% to 99%?
 How would the confidence interval change if the
sample size had been 200 instead of 150?
 How would the confidence interval change if the
standard deviation had been 0.61 instead of 0.41?
Example
In a survey of 517 music teachers, 403 said that the video
games Guitar Hero and Rock Band have a positive
effect on music education.
 Construct and interpret a 99% confidence interval for
the percentage of music teachers who believe that
these video games have a positive effect.
We are 99% confident that the population percentage of
music teachers who believe that Guitar Hero and Rock
Band have a positive effect on music education is
between 73.2% and 82.6%.