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PERT

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CPM vs. PERT

In 1957 the Critical Path Method (CPM) wasdeveloped as a network odel !or pro"ectana#eent.It is a deterinistic ethod that $ses a !i%edtie estiate !or each activit&.'hile CPM is eas& to $nderstand and $se butdoes not consider uncertainty in activity time

estiation.Uncertainty : weather, equipment failure,absenteeism can have a #reat ipact on thecopletion tie o! a cople% pro"ect.

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PERT

The Program Evaluation and ReviewTechnique(PERT) is a network odel thatallows !or randoness in activit&

copletion ties.enerall& $sed when there is a risk o! tieassociated with pro"ect.

R * + pro"ects where correct tiedeterinations cannot ,e ade.

E%aple - Pro"ect on la$nchin# the spacecra!t.

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PERT

PERT was developed in the late 195/s !orthe 0.. 2av&/s Polaris ,allistic issiles&ste pro"ect havin# tho$sands o!

contractors.This pro"ect was nota,le in that it !inished13 onths ahead o! sched$le and within

,$d#et.It has the potential to red$ce ,oth the tieand cost re4$ired to coplete a pro"ect.

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PERT

This ethod $ses statistical tools !orIplication o! $ncertainties on pro"ect tie

r

tochastic Modelin# o! 2etwork

6 distin#$ishin# !eat$re o! PERT is itsa,ilit& to deal with $ncertaint& in activit&

copletion ties.or each activit& the odel $s$all&incl$des three tie estiates-

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Three Tie Estiates

1

8

:5

8;5;18

:;7;1 hortest possi,le tie in which anactivit& can ,e copleted $nder ideal conditions.This is denoted ,& to

Pessimistic time; the lon#est tie that an activit&i#ht re4$ire. I! ever&thin# went wron# anda,noral sit$ation prevails.however it doesn/t?tincl$de hi#hl& $n$s$al catastrophies s$ch as

earth4$ake !loods !ires. It is denoted ,& tp

Most likely time(Most re4$ent;Mode); thecopletion tie havin# the hi#hest pro,a,ilit&.2oral condition prevails. It is denoted ,& t

=

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1

8

:5

8;5;18

:;7;1