Question 15 6 pts Battery Lives: Twenty batteries were tested to see how many hours they would last. The frequency distribution is shown below. Number of Hours Frequency 1-3 4 4-6 8 7-9 5 10-12 1 13-15 2 Compute the standard deviation and round the answer to 2 decimal n - ( E f . X ? ) - ( E f . x ) places. Use the formula s = 1 where f is the n(n-1) frequency and X is the midpoint. NOTE: You may use the 1-Var Stat function on the graphing calculator to compute the sample standard deviation