Time Management Flashcards
Start-Finish Types
Finish-to-Start(FS):
An activity must finish before the successor can start. (dig hole; plant tree)(most common)
Start-to-Start (SS): An activity must start before the successor can start.
Finish-to-Finish (FF): An activity must finish before the successor can finish.
Start-to-Finish (SF): An activity must start before the successor can finish. (rarely used)
Lead
A lead can be added to start an activity before completion of the predecessor
(Ex: Start writing Training Material before completion of Testing)
Lag
A lag is inserted waiting time b/w activities
(Ex: needing to wait 3 days after pouring concrete before constructing the frame of the house)
Triangular Distribution / 3P Estimate
Weighted 3P Estimate / PERT (Program
Evaluation & Review Technique) / Expected
Value (modified BETA distribution)
Standard Deviation (σ)
Variance (v)
(P + M + O) / 3
(P + 4M + O) / 6
σ = (P - O) / 6
v = ((P - O) / 6) ^2
Duration/Cost :– * P – Pessimistic; M - Most Likely (Realistic); O – Optimistic
* PERT is probabilistic, using statistical estimates of durations (left)
* Estimate range for an activity = PERT duration +/- standard deviation
* Std deviation tells the amt of uncertainty/risk involved in the estimate for the activity
* There is 68% probability that the work will finish within +/- one std deviation (1 σ)
* There is 95% probability that the work will finish within +/- two std deviations (2 σ)
* There is 99% probability that the work will finish within +/- three std deviations (3 σ)
Total Float / Slack
(LS – ES) or (LF - EF)
There is a start formula & a finish formula; Both begin with Late
Activity Duration
(EF – ES) or (LF – LS)
Finish - Start for both Early and Late groups
Forward Pass
EF = (ES + Duration - 1)
(Add 1 day to Early Start)
Backward Pass
LS = (LF - Duration + 1)
Develop Schedule Process – Critical Path Method
CPM is deterministic, using specific durations