Mechanical Engineering - Industrial Engineering and Production Management - Discussion
Discussion Forum : Industrial Engineering and Production Management - Section 2 (Q.No. 6)
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
Discussion:
27 comments Page 1 of 3.
UCHIHA said:
7 years ago
Explanation for z=1.
Remember normal curve is symmetrical hence for z=0 the probability is 50%
now if you see chart for 6σ, it is 99.97%, for 4σ it is 95.95% and for 2σ it is 68%.
For 6σ it implies 3σ on both sides of z=0 line on a normal curve and that implies z=3.
Hence for z=1, it implies 1σ and for 1σ it is 68/2=34%,
Hence we go here for z=1 as 50%+34%=84%,
Henceforth remember it!
Remember normal curve is symmetrical hence for z=0 the probability is 50%
now if you see chart for 6σ, it is 99.97%, for 4σ it is 95.95% and for 2σ it is 68%.
For 6σ it implies 3σ on both sides of z=0 line on a normal curve and that implies z=3.
Hence for z=1, it implies 1σ and for 1σ it is 68/2=34%,
Hence we go here for z=1 as 50%+34%=84%,
Henceforth remember it!
(3)
Mastan said:
6 years ago
@All.
Here standard deviation means "sigma".
Here standard deviation means "sigma".
(1)
Pawan said:
6 years ago
Yeah, 0.66 is right the right one.
(1)
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.
Standard deviation 1+2+2=5,
20-17/5=0.6.
So, I think the answer is 0.66.
(1)
Nerellakarthik said:
8 years ago
What is Z table?
Chandu said:
2 years ago
Z = (20-17)/√(1²+2²+2²),
Z = (20-17)/3,
Z = 1,
So P(1)= 0.842.
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.
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.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers