Which one of the following statements is correct?
- APERT is commonly used in the construction work.
- BPERT is suitable for the estimation of activity duration where high levels of uncertainty is there.Correct
- CPERT does not provide time duration.
- DPERT is a deterministic approach for estimating the time duration of an activity.
Solution
Concept
PERT is a probabilistic method. It uses three time estimates, so it suits activities with high uncertainty.
Formula
te = (to + 4tm + tp)/6 ; σ = (tp - to)/6
Step-by-step solution
1. PERT uses three time estimates: optimistic (to), most likely (tm) and pessimistic (tp). 2. It finds expected time te and its variance, so it is probabilistic. 3. A probabilistic method is used when activity durations are uncertain, for example in R&D or new projects. 4. So statement B is correct.
Explanation
PERT is event oriented and probabilistic. It is used when activity time cannot be fixed exactly, as in research or new type of work. Repetitive construction work, where times are well known, normally uses CPM.
Why the other options are wrong
A: Construction work mostly uses CPM, not PERT. C: PERT does give time duration (expected time te and project duration). D: PERT is probabilistic. CPM is the deterministic method.
Shortcut
PERT = Probabilistic (uncertain time). CPM = deterministic (known time, cost-time trade-off).
Common mistake
Students mix up PERT and CPM and call PERT deterministic.
Correct answer: B) PERT is suitable for the estimation of activity duration where high levels of uncertainty is there.