9514 1404 393
Answer:
68%
Explanation:
According to the empirical rule, 68% of the distribution lies within 1 standard deviation of the mean.
Here, the mean is 20 and the standard deviation is 5. The bounds on 1 standard deviation from the mean are 20±5 = [15, 25]. This is precisely the interval of interest.
68% of students wait between 15 and 25 minutes