The intersection of Bulldog Ave and State St has had 85 righ

The intersection of Bulldog Ave and State St has had 8.5 right-angle crash rate per million entering vehicles (RMEV) during the last 3 years. For statistic purposes, we have 10 intersections other than this intersection that have characteristics similar to this intersection. Their crash rates for the last 3 years are shown in the table below. Does this intersection have an unusually high crash rate than the control stations?

Right-angle crash rate Mean Standard Dev 7.4 x 10 1.5 x 10

Solution

See that if rmev per million at intersection of Bulldog Ave and State St exceed the value (mean + 3*standard drviation)

than only we can conclude that intersection have an unusually high crash rate than the control stations.

But here,mean + 3*standard drviation=7.4 + 1.5*3=11.9 (>8.5)

Hence, no intersection have no unusually high crash rate than the control stations.

*hope you like the solution*