Page 16 - OPERATIONS RESEARCH

Thus we have, te= 1/3[2t + (t +t )/2] = (t + 4 t +t )/6.
p
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m
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p
Standard deviation 6σ=t –t or σ = (t –t )/6.
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Variance σ = {(t − t )/6} .
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2
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PROBABILITY OF MEETING THE SCHEDULE TIME
The probability of completing the project by time (Ts) is given by,
Prob [Z<{(Ts – Te)/σ }]
e
Standard normal variate (SNV) is given by,
Z = {[Ts – Te]/σ }
e
EXAMPLE
A project consists of eight activities with the following relevant information:
Activity Immediate Estimated Duration (days)
predecessor Optimistic(t ) Most likely( t ) Pessimistic(t )
p
m
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A - 1 1 7
B - 1 4 7
C - 2 2 8