# Disecrete Probability Distributions Help Needed

• Apr 2nd 2008, 06:30 PM
dasani
Disecrete Probability Distributions Help Needed

1. Survey conducted showed that the average commuter spends about 26 min on a one-way door-to-door trip. Also 5% of commuters reported a one-way commute of over an hour.

a. If 20 commuters are surveyed, what is the probability that three will report a one-way commute of more than one hour?
b. If a company has 2000 employees, what is the expected number of employees with a commute of more than one hour?

2. XYZ Corp. plans to interview Internet users to learn how its proposed Web site will be received by different age groups. 40% of individuals ages 18-54 and 12% age 55 and over use the Internet.

a. How many people from the 18-54 need to be contacted to find an expected number of 10 Internet users?
• Apr 2nd 2008, 08:23 PM
CaptainBlack
Quote:

Originally Posted by dasani

1. Survey conducted showed that the average commuter spends about 26 min on a one-way door-to-door trip. Also 5% of commuters reported a one-way commute of over an hour.

a. If 20 commuters are surveyed, what is the probability that three will report a one-way commute of more than one hour?

The number of commuters who report more than 1 hour has a binomial distribution B(20,0.05), so:

p(3)=b(3;20,0.05)

Quote:

b. If a company has 2000 employees, what is the expected number of employees with a commute of more than one hour?
5% of them

RonL
• Apr 2nd 2008, 08:25 PM
CaptainBlack
Quote:

Originally Posted by dasani

2. XYZ Corp. plans to interview Internet users to learn how its proposed Web site will be received by different age groups. 40% of individuals ages 18-54 and 12% age 55 and over use the Internet.

a. How many people from the 18-54 need to be contacted to find an expected number of 10 Internet users?

Let the number of 18-54 year olds contacted be N, expected number of internet users ia $N \times 0.40 = 10$

RonL