Chapter 8 Estimating with Confidence

 A point estimator is a statistic that provides an estimate of a population parameter. The value of that statistic from a sample is call a point estimate.  Ideally, a point estimate is our “best guess” at the value of an unknown parameter.  Example: Tonya wants to estimate what proportion of students are going to attend the prom. She interviews a SRS of 50 of the 750 students at her school and finds that 36 of them are going to the prom. What is the point estimator? Definitions

To say that we are 95% confident is shorthand for “95% of all possible samples of a given size from this population will result in an interval that captures the unknown parameter.” Confidence Interval

Confidence Intervals

 Conditions for constructing confidence interval:  Random  Normal  Independent – Individual observations are independent. (sample size n should be no more that 10% of the pop) Conditions

8.2 Proportions

 So z* for our problem is _____  Confidence interval: Keep going…

Sample Sizes

 Determine the sample size needed to estimate p within 0.03 with 95% confidence. Example

 Pg. 481 (16, 17, 21-24)  Pg. 496 (27-33, 40, 42, 44-47, 49-52) Homework