Question

Question 1

2 pts

(09.05)

At an intersection, the red light times are normally distributed

with a mean time of 3 minutes and a standard deviation of 0.25

minutes. Approximately what percent of red lights last between

2.5 and 3.5 minutes? (2 points)

32%

68%

Answer 1

Answer: The percent of red lights last between 2.5 and 3.5 minutes = 95.44% approx.

Explanation:

Given: Mean time = 3 minutes

standard deviation = 0.25 minutes

The probability of red lights last between 2.5 and 3.5 minutes :-

`P(2.5<x<3.5)\\\\=P((2.5-3)/(0.25)<(x-\mu)/(\sigma)<(3.5-3)/(0.25))\\\\=P(-2<z<2)\\\\=2P(Z<2)-1\\\\=2(0.9772)-1\\\\=0.9544`

The percent of red lights last between 2.5 and 3.5 minutes = 95.44% approx.