Chapter Goals
     After completing this chapter, you should be able to: 
      Distinguish between a point estimate and a confidence 
        interval estimate
      Construct and interpret a confidence interval estimate for a 
        single population mean using both the z and t distributions
      Determine the required sample size to estimate a single 
        population mean or a proportion within a specified margin 
        of error
      Form and interpret a confidence interval estimate for a 
        single population proportion
                                                                         8-2
                   Overview of the Chapter
         Builds upon the material from Chapter 1 and 7
         Introduces using sample statistics to estimate population 
           parameters
                     Because gaining access to population parameters can be 
                      expensive, time consuming and sometimes not feasible
         Confidence Intervals for the Population Mean, μ
             when Population Standard Deviation σ is Known
             when Population Standard Deviation σ is Unknown
         Confidence Intervals for the Population Proportion, p
         Determining the Required Sample Size for means and 
           proportions
                                                                                  8-3
                       Estimation Process
                                                         Confidence Level
                           Random Sample Mean
                              (point estimate)
                                                          I am 95% 
         Population                                       confident that 
                                  Mean                    μ is between 
         (mean, μ, is                x = 50               40 & 60.
          unknown)
           Sample                                            confidence
                                                               interval
                                                                            8-4
                               Point Estimate
         Suppose a poll indicate that 62% (sample mean) of the 
           people favor limiting property taxes to 1% of the market 
           value of the property. 
             The 62% is the point estimate of the true population of people 
               who favor the property-tax limitation. 
             EPA tested average Automobile Mileage (point estimate)
                                                                                    8-5
                       Confidence Interval
      The point estimate (sample mean) is not likely to exactly 
        equal the population parameter because of sampling error.
          Probability of “sample mean =  population mean” is zero
      Problem: how far the sample mean is from the 
        population mean.
      To overcome this problem, “confidence interval” can be 
        used as the most common procedure.
                                                                            8-6