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# Exponential Distribution using Excel

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The useful life of an electrical component is exponentially distributed with a mean of 2,500 hours.

a. what is the probability the circuit will last more than 3,000 hours

b. what is the probability the circuit will last between 2,500 and 2,750 hours.

c. what is the probability the circuit will fail within the first 2,000 hours.

https://brainmass.com/physics/circuits/325950

#### Solution Preview

The answers are in the attached Excel file

The useful life of an electrical component is exponentially distributed with a mean of 2,500 hours.
a. what is the probability the circuit will last more than 3,000 hours

We first need to calculate the probability of circuit failing between 0 and 3,000 hours

x= 3,000 hours
mean= 2,500 hours
lambda= 0.0004 = 1 / 2500
cumulative = 1

Probability of failure between 0 and 3,000 hours= 0.6988 = EXPONDIST(3000 , 0.0004 , ...

#### Solution Summary

Exponential Probability calculations using Excel worksheet function EXPONDIST.

\$2.19

## 12 Multiple Choice Word Problems involving the Binomial, Normal, Poisson and Exponential Probability Distributions

Need some assistance with the following questions.

A student has an important exam coming up and is contemplating not studying for the exam in order to attend a party with his friends. The student must earn a minimum score of 70% on the exam in order to successfully maintain his desired GPA. Suppose the student knows in advance that the exam will consist of twenty multiple choice questions with four possible answers for each question. Answer questions 1-3 using the preceding information and modeling this situation as a binomial distribution.

1. What is the probability that the student will successfully earn exactly the required minimum score of 70% on the exam based solely upon randomly guessing the correct answer for each question?
o 2.57
o 2.57E-02
o 2.57E-05
o 2.57E-04

2. What is the probability that the student will earn less than the required minimum score of 70% on the exam based solely upon randomly guessing the correct answer for each question?
o 0.74673
o 0.85198
o 0.99997
o 0.23499

3. What is the probability that the student will successfully earn no less than the required minimum score of 70% on the exam based solely upon randomly guessing the correct answer for each question?
o 3.51E-04
o 2.95E-05
o 6.87E-06
o 1.27E-03

The mean time required to complete a certain type of construction project is 52 weeks with a standard deviation of 3 weeks. Answer questions 4-7 using the preceding information and modeling this situation as a normal distribution.

4. What is the probability of the completing the project in no more than 52 weeks?
o 0.25
o 0.50
o 0.75
o 0.05

5. What is the probability of the completing the project in more than 55 weeks?
o 0.2743
o 0.5091
o 0.7511
o 0.0546

6. What is the probability of completing the project between 56 weeks and 64 weeks?
o 0.2587
o 0.3334
o 0.5876
o 0.0911

7. What is the probability of completing the project within plus or minus one standard deviation of the mean?
o 0.951
o 0.852
o 0.759
o 0.683

Customers arrive at a supermarket check-out counter with an average arrival rate of 9 customers per hour. Answer questions 8-10 using the preceding information and modeling this situation as a Poisson distribution.

8. What is the probability of less than 5 customers arriving at the supermarket check-out counter in a given one hour period?
o 0.054
o 0.446
o 0.359
o 0.612

9. What is the probability of exactly 12 customers arriving at the supermarket check-out counter in a given one hour period?
o 0.262
o 0.044
o 0.073
o 0.189

10. What is the probability of no less than 12 customers arriving at the supermarket check-out counter in a given one hour period?
o 0.115
o 0.197
o 0.381
o 0.686

A local commuter bus service advertises that buses run every twelve minutes along a certain route. Answer questions 11and 12 using the preceding information and modeling this situation as an exponential distribution.

11. What is the probability of a bus picking up the passengers at a given bus stop in less than or equal to 12 minutes following their arrival at the bus stop?
o 0.519
o 0.632
o 0.466
o 0.772

12. What is the probability of a bus picking up the passengers at a given bus stop in more than 15 minutes following their arrival at the bus stop?
o 0.287
o 0.343
o 0.541
o 0.119

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