Page 18 - OPERATIONS RESEARCH

From the above network diagram, we observe:

CPM: 1->3->5->6->7 OR B->E->G->H.
Expected duration of the project is 19 days.

The variance of the project length is: σ =1+4+4+0.1 =1+4+4+0.108 = 9.108.
2
Or σ = √9.108= 3.02.
e
P(z≤ 1.645)=0.5 + 0.45 = 0.95.
And then, (Ts – Te)/σ =1.645.
e
Or Ts=19+3.02×1.645=24 days.
Hence, 24 days of project completion time will have 95% confidence of completion in the

scheduled time.

iii. When the average duration of activity F increases to 14, the path C->F->H also
becomes critical. The standard deviation of new critical path is :

σ = √9. 108+2=3.36.
e
P(z<1.645)= 0.95 gives us (Ts – 19)/3.36=1.645.
Ts = 19 + 3.36 ×1.645 = 24.52 days.

Hence the project completion duration of 24.52 days will have 95% confidence.

DISTINCTION BETWEEN PERT ND CPM:

Both PERT and CPM are managerial techniques for planning and control of large

complex projects. Both are techniques to network analysis a network is prepared to analyze inter-