# 8: Confidence Intervals

- Page ID
- 697

In this chapter, you will learn to construct and interpret confidence intervals. You will also learn a new distribution, the Student's-t, and how it is used with these intervals. Throughout the chapter, it is important to keep in mind that the confidence interval is a random variable. It is the population parameter that is fixed.

- 8.1: Prelude to Confidence Intervals
- In this chapter, you will learn to construct and interpret confidence intervals. You will also learn a new distribution, the Student's-t, and how it is used with these intervals. Throughout the chapter, it is important to keep in mind that the confidence interval is a random variable. It is the population parameter that is fixed.

- 8.2: A Single Population Mean using the Normal Distribution
- A confidence interval for a population mean with a known standard deviation is based on the fact that the sample means follow an approximately normal distribution.

- 8.3: A Single Population Mean using the Student t-Distribution
- We rarely know the population standard deviation. In the past, when the sample size was large, this did not present a problem to statisticians. They used the sample standard deviation ss as an estimate for σσ and proceeded as before to calculate a confidence interval with close enough results. However, statisticians ran into problems when the sample size was small. A small sample size caused inaccuracies in the confidence interval.

- 8.4: A Population Proportion
- The procedure to find the confidence interval, the sample size, the error bound, and the confidence level for a proportion is similar to that for the population mean, but the formulas are different.

- 8.5: Confidence Interval - Home Costs (Worksheet)
- A statistics Worksheet: The student will calculate the 90% confidence interval for the mean cost of a home in the area in which this school is located. The student will interpret confidence intervals. The student will determine the effects of changing conditions on the confidence interval.

- 8.6: Confidence Interval -Place of Birth (Worksheet)
- A statistics Worksheet: The student will calculate the 90% confidence interval the proportion of students in this school who were born in this state. The student will interpret confidence intervals. The student will determine the effects of changing conditions on the confidence interval.

- 8.7: Confidence Interval -Women's Heights (Worksheet)
- A statistics Worksheet: The student will calculate a 90% confidence interval using the given data. The student will determine the relationship between the confidence level and the percentage of constructed intervals that contain the population mean.

- 8.E: Confidence Intervals (Exercises)
- These are homework exercises to accompany the Textmap created for "Introductory Statistics" by OpenStax.

- 8.S: Confidence Intervals (Summary)
- In this module, we learned how to calculate the confidence interval for a single population mean where the population standard deviation is known.

### Contributors

Barbara Illowsky and Susan Dean (De Anza College) with many other contributing authors. Content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/30189442-699...b91b9de@18.114.