Question

according to the los angeles times, speed limits on california highways are set at the 85th percentile of vehicle speeds on those stretches of road. explain to someone who knows little statistics what that means.
the speed limit is set at the value that will be 0.85 standard deviations above the mean.
the speed limit is set at the value that will have 85% of the vehicles on that road traveling at a speed less than the speed limit.
the speed limit is set at the value that will have 85% of the vehicles on that road traveling at a speed greater than the speed limit.
the speed limit is set at the value that will have 15% of the vehicles on that road traveling at a speed less than the speed limit.

Explanation:

The p - th percentile of a data - set is a value such that p percent of the data values are less than or equal to that value. So, the 85th percentile of vehicle speeds means that 85% of the vehicles on the road are traveling at a speed less than the speed limit.

Answer:

The speed limit is set at the value that will have 85% of the vehicles on that road traveling at a speed less than the speed limit.