Chapter 3 - Statistics for Describing, Exploring, and Comparing Data - 3-3 Measures of Variation - Basic Skills and Concepts - Page 111: 41

a) 95% b)68%

a) By the empirical rule, 95% of the data are within 2 standard deviations of the mean, hence the answer is 95%. b) $|280-215|=|280-345|=65=standard \ deviation$, hence by the empirical rule, 68% of the data are within 1 standard deviation from the mean, hence the answer is 68%.