MATH225
Confidence Intervals for the Mean (Population Standard
Deviation Known)
Population Point Estimate
Mean = 𝜇 Mean = 𝑥̅
Population Proportion = p Sample Proportion = 𝑝̂
Review
Example: The average number of chips per bag from the potato chips available at a
supermarket is unknown. A random sample of potato chip bags from the
supermarket yields a sample man of 250.6 chips. Assume the sample distribution of
the mean has a standard deviation of 18.9.
Use the Empirical Rule to construct a 99.7% confidence interval for the true
population mean number of potato chips.
**The your confidence level…the your confidence interval.
1
, Example:
Example: A random sample of registered voters were asked about an issue on the
ballot of an upcoming election. The proportion of those surveyed who plan to vote
“Yes” oh the issue is 0.54, with a margin of error of 0.06.
Construct a confidence interval for the proportion of registered voters that plan to
vote “Yes” on the issue.
2
Confidence Intervals for the Mean (Population Standard
Deviation Known)
Population Point Estimate
Mean = 𝜇 Mean = 𝑥̅
Population Proportion = p Sample Proportion = 𝑝̂
Review
Example: The average number of chips per bag from the potato chips available at a
supermarket is unknown. A random sample of potato chip bags from the
supermarket yields a sample man of 250.6 chips. Assume the sample distribution of
the mean has a standard deviation of 18.9.
Use the Empirical Rule to construct a 99.7% confidence interval for the true
population mean number of potato chips.
**The your confidence level…the your confidence interval.
1
, Example:
Example: A random sample of registered voters were asked about an issue on the
ballot of an upcoming election. The proportion of those surveyed who plan to vote
“Yes” oh the issue is 0.54, with a margin of error of 0.06.
Construct a confidence interval for the proportion of registered voters that plan to
vote “Yes” on the issue.
2
