## Chapter 19 Powerpoint Outline

Stats: Modeling the World Chapter 19 Confidence Intervals for Proportions Making an educated guess? Rarely do we actually know information about our population. Usually we: - take a sample - find a sample statistic - make a guess about the true parameter value Our guess will be a bit off, this is the idea of a confidence interval. The sample proportion ? Recall from Chapter 18 that the sampling distribution model of ? is centered at p, with standard deviation . Since we don?t know p, we can?t find the true standard deviation of the sampling distribution model, so we need to find the standard error: The Empirical Rule Revisited? By the 68-95-99.7% Rule, we know - about 68% of all samples will have ? ?s within 1 SE of p