Question

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? a) 0.25 b) 0.50 c) 0.75 d) 0.05

5. What is the probability of the completing the project in more than 55 weeks? a) 0.1587 b) 0.5091 c) 0.7511 d) 0.0546

6. What is the probability of completing the project between 56 weeks and 64 weeks? a) 0.2587 b) 0.3334 c) 0.5876 d) 0.0911

7. What is the probability of completing the project within plus or minus one standard deviation of the mean? a) 0.951 b) 0.852 c) 0.759 d) 0.683

Answer 1

Let X be the time required to complete a certain type of construction project. X has normal distribution with mean and standard deviation

4. What is the probability of the completing the project in no more than 52 weeks?

ans: b) 0.50

5. What is the probability of the completing the project in more than 55 weeks?

ans: a) 0.1587

6. What is the probability of completing the project between 56 weeks and 64 weeks?

Due to the rounding errors, we can pick the closest answer as 0.0911

ans: d) 0.0911

7. What is the probability of completing the project within plus or minus one standard deviation of the mean?

ans: d) 0.683