Chapter 12 - Data Analysis and Probability - 12-7 Theoretical and Experimental Probability - Practice and Problem-Solving Exercises - Page 774: 40

$\frac{3}{10}$

P(event)=$\frac{numberoffavorableoutcomes}{numberofpossibleoutcomes}$ There are 20 differences from the stem and leaf plot so this is the number of possible outcomes. Out of the 20, six are from 10 to 15 points:10, 11, 12,13, 14,15, so this is the number of favorable outcomes. So, the probability is: P(10-15 points)=$\frac{6}{20}$ -simplify- P(10-15 points)=$\frac{3}{10}$