1. Confidence Interval on Vacation “Can we buy an RV?” “Why?” “Everyone else does!” “Really!?” Time: Aug, 1990 Place: Campground

2. Let us collect some data! My Favorite Recipe :  Question  Data  Analysis  Conclusion

3. Question: “Does everyone else have RV’s?” If p>0.5, we will buy an RV! Data: To and from Yellowstone, tallied all vehicles in the opposite direction. Decision Through Data!

4. Original Data Collection Sheets

5. Analysis: x = 67 RV’s n = 857 vehicles sample proportion is: CI for p is: Conclusion: There is strong evidence for p<0.5. Less than 50% people have RV’s! $ saved!

6. Analysis: x = 67 RV’s n = 857 vehicles We want 95% confidence. Conclusion: We are 95% Confident that the true p = (0.078±0.018)! Only 6% to 9.6% people have RV’s! $ saved! Confidence Interval to find the true proportion of RV’s: p = ?