Question

Setting speed limits 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.

Short answer

$15\%$ of the data is greater than or equal to the data point. The speed limits are established at the speed at which $85$ percent of vehicle speeds are below the speed limit.

Step-by-step solution

Part (a) Step 1: Given information

On California highways, vehicle speed limits are established at the $85th$ percentile for specific lengths of road.

Concept

The percentile of an individual is the percentage of the distribution that is less than the data value of the individual.

Explanation

The $85th$ percentile is a data point in which $85$ percent of the data is less than or equal to the data point, and $15\%$ of the data is higher than or equal to the data point. On some stretches of road, the speed limits are established at the speed at which $85$ percent of vehicle speeds are below the speed limit.