Problem 7) (Inverse N calculation) Consider the 68-95-99.7 rule. 95% of the observations in a N distribution are within u + 20. Where does the "2" come from? Find the z scores for the central 0.95 area under the normal curve. Sketch a normal curve, showing areas and z scores. Are those z scores close to -2 and +2? > 0. 68 0. 16 10. 16 What is the z score for the area in the left tail? Look up the area of 0.16 in the Normal table and find that z = -0.99, or approximately -1. See next page