Chapter 8 - Confidence intervals. After mastering the material in this chapter, you will be able to: Calculate and interpret a z-based confidence interval for a population mean when σ is known, describe the properties of the t distribution and use a t table, calculate and interpret a t-based confidence interval for a population mean when σ is unknown,. | Chapter 8 Confidence Intervals Copyright © 2014 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin Confidence Intervals z-Based Confidence Intervals for a Population Mean: σ Known t-Based Confidence Intervals for a Population Mean: σ Unknown Sample Size Determination Confidence Intervals for a Population Proportion Confidence Intervals for Parameters of Finite Populations (Optional) 8- z-Based Confidence Intervals for a Mean: σ Known Confidence interval for a population mean is an interval constructed around the sample mean so we are reasonable sure that it contains the population mean Any confidence interval is based on a confidence level LO8-1: Calculate and interpret a z-based confidence interval for a population mean when σ is known. 8- General Confidence Interval In general, the probability is 1 – α that the population mean μ is contained in the interval The normal point zα/2 gives a right hand tail area under . | Chapter 8 Confidence Intervals Copyright © 2014 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin Confidence Intervals z-Based Confidence Intervals for a Population Mean: σ Known t-Based Confidence Intervals for a Population Mean: σ Unknown Sample Size Determination Confidence Intervals for a Population Proportion Confidence Intervals for Parameters of Finite Populations (Optional) 8- z-Based Confidence Intervals for a Mean: σ Known Confidence interval for a population mean is an interval constructed around the sample mean so we are reasonable sure that it contains the population mean Any confidence interval is based on a confidence level LO8-1: Calculate and interpret a z-based confidence interval for a population mean when σ is known. 8- General Confidence Interval In general, the probability is 1 – α that the population mean μ is contained in the interval The normal point zα/2 gives a right hand tail area under the standard normal curve equal to α/2 The normal point -zα/2 gives a left hand tail area under the standard normal curve equal to a/2 The area under the standard normal curve between zα/2 and zα/2 is 1 – α LO8-1 8- General Confidence Interval Continued If a population has standard deviation σ (known), and if the population is normal or if sample size is large (n 30), then a (1-a)100% confidence interval for m is LO8-1 8- t-Based Confidence Intervals for a Mean: σ Unknown If σ is unknown (which is usually the case), we can construct a confidence interval for μ based on the sampling distribution of If the population is normal, then for any sample size n, this sampling distribution is called the t distribution LO8-2: Describe the properties of the t distribution and use a t table. 8- The t Distribution The curve of the t distribution is similar to that of the standard normal curve Symmetrical and bell-shaped The t distribution is more spread out than