Question

The average commute to work (one way) is 25 minutes according to the 2005 American Community Survey. If we assume that commuting times are normally distributed and that the standard deviation is 6.1 minutes, calculate the probability that a randomly selected commuter spends for the following cases.

1. More than 31 minutes commuting one way.
2. Less than 8 minutes commuting one way.

Answer 1

1. 0.1635

2. 0.0026

Explanation:

The computation of the probability in the following cases are as follows:

1.

Given that

Mean = 25 minutes

ANd, the standard deviation is 6.1 minutes

So here the z score would be

= (31 - 25) ÷(6.1)

= 0.98

Now the probability is

= P(Z>0.98)

= 0.1635

2. the z score would be

= (8 - 25) ÷(6.1)

= -2.79

Now the probability is

= P(Z<-2.79)

= 0.0026