Statistics probability - normal distribution questions?
For a car traveling 60 kilometers per hour (km/h), the distance required to brake to a stop is normally distributed, with mean of 20 meters and a standard deviation of 2.4 meters. Suppose you are traveling 60 km/h in a residential area and a car moves abruptly into your path at a distance of 20 m.
(a) If you apply your brakes, what is the probability that you will brake to a stop within
18m or less?
(b) What is probability that you will avoid collision?
How would I solve these?
- Mike GLv 76 months agoFavorite Answer
μ = 20
σ = 2.4
a) z(X=18) = (18-20)/2.4 = -0.8333
From the z-tables
P(z<-0.8333) = 0.2033
b) To avoid a collision X < 20 m
z = 0
P(z<0) = 0.5000
- 6 months ago
Find the z-score
(18 - 20) / 2.4 = -2/2.4 = -10/12 = -5/6 = -0.833333
0.2033, or 20.33% of the area lies to the left of 18. You have about a 20.33% chance of stopping in 18 meters or less
You need to stop in 20 meters or less and 50% of the graph lies to the left of the 20m mark on the curve. You have a 50% chance of avoiding the collision