The amount of time workers spend commuting to their jobs each day in a large metropolitan city has a mean of 70 minutes and a standard deviation of 20 minutes. Assuming nothing is known about the shape of the distribution of commuting times, what percentage of these commuting times are between 30 and 110 minutes?
A) at least 75%
B) at least 89%
C) at least 0%
D) at least 95%

Question

Quizplus · Accepted Answer

According to Chebyshev's theorem, at least 75% of data lies within two standard deviations of the mean for any distribution. Here, 30 to 110 minutes is within two standard deviations (70 ± 2*20).

The Amount of Time Workers Spend Commuting to Their Jobs