Question 1048067
There were 30, and 21 or 70% were longer than 8 minutes (strictly speaking 20 were, since the 21st was 8 minutes exactly).  That would be 2/3s.
The mean is 10.26 with sd 4.29 (treated as a sample, dividing by 29).
Within 1 sd is (5.97,14.55) are 21 or 70%, certainly consistent with the empirical rule.
Within 2 sd is (1.68,18.84) are 29/30 or 96.7%, again consistent with the empirical rule.