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Mechanical Engineering - Industrial Engineering and Production Management - Discussion

Discussion Forum : Industrial Engineering and Production Management - Section 2 (Q.No. 6)
Industrial Engineering and Production Management
6.
A PERT network has three activities on critical path with mean time 3, 8 and 6 and standard deviations 1, 2 and 2 respectively. The probability that the project will be completed in 20 days is
0.50
0.66
0.84
0.95
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
27 comments Page 1 of 3.
Chandu said:   2 years ago
Z = (20-17)/√(1²+2²+2²),
Z = (20-17)/3,
Z = 1,
So P(1)= 0.842.
Shahid Shafi said:   3 years ago
Here, 20-17/5 = 0.66.
Debaduyti Nath said:   5 years ago
Agree @Chigumbura and @Uchiha.

In PERT analysis, the time estimates of activities and probability of their occurrence follow Bet Distribution Curve.

But Expected project duration generally follows the Normal Distribution Curve.
The answer is 0.84.
Amrit kshetri said:   6 years ago
But PERT network follows beta probability distribution. So can concept of normal distribution curve be applied here?
Midhunlal said:   6 years ago
Standard deviation equal to square root of variance. Sahir standard deviation is given directly so no need to take root.
Kapilkotadiya said:   6 years ago
It is working on the function of Z which is denoted by Z(1)=0.84, therefore the answer is 0.84.

Thanks.
Mastan said:   6 years ago
@All.

Here standard deviation means "sigma".
(1)
Pawan said:   6 years ago
Yeah, 0.66 is right the right one.
(1)
Sumit Patil said:   7 years ago
Yeah, 0. 66 is right. I agree @Nir.
Nir said:   7 years ago
3+8+6=17.

Standard deviation 1+2+2=5,
20-17/5=0.6.
So, I think the answer is 0.66.
(1)
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