The average speed cars travel on a road is 77 km/h.A car travelling 60 km/h has a z-score of -1.7.Find the standard deviation.
A)40 km/h
B)10 km/h
C)30 km/h
D)0.5 km/h
E)1 km/h

Question

Quizplus · Accepted Answer

We know that the average speed of cars on the road is 77 km/h. We also know that a car traveling 60 km/h has a z-score of -1.7.

Using the formula for z-score, we can calculate the difference between the car's speed and the average speed of cars on the road in terms of standard deviations:

z = (x - μ) / σ

where x is the car's speed, μ is the average speed of cars on the road, and σ is the standard deviation.

Substituting the given values, we get:

-1.7 = (60 - 77) / σ

Solving for σ, we get:

σ = (60 - 77) / -1.7

σ ≈ 10

Therefore, the standard deviation of the speeds of cars on the road is approximately 10 km/h. The best choice is B) 10 km/h.

The Average Speed Cars Travel on a Road Is 77