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LECTURE 4. FLOATS AND FLOAT CALCULATIONS. Floats. Total Float (TF) Free Float (TF) Interfering Float (INTF) Independent Float (INDF) Start Float (SF) Finish Float (FNF). Total Float. Total Float is the amount of time an activity can delay but not delay the termination of the project
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Floats • Total Float (TF) • Free Float (TF) • Interfering Float (INTF) • Independent Float (INDF) • Start Float (SF) • Finish Float (FNF)
Total Float • Total Float is the amount of time an activity can delay but not delay the termination of the project • TFi = LSj – ESi
What are A,B and C’s Total Float? TFA = 5-2 = 3 TFB = 7-5 = 2 TFC = 9-6 = 3
Free Float? • Free Float is the amount of time an activity can delay but not delay the termination of the project nor delay the start of any following activity • FFi = Min ESj – EFi , j
What is A’s Free Float? FFA = Min [(5-4), (6-4)] FFA = 1
Interfering Float • Interfering Float is the time span in which the completion of an activity may occur and not delay the termination of the project, but within which completion will delay the start of some following activity • The portion of total float which affects other activities but not the project finish date. • INTFi = TFi – FFi
What is A’s interfering float? TFA = 3 FFA = 1 INTFA = 3-1 = 2
Independent Float • Independent Float is the time an activity might delay and not delay the termination of the project, not delay the start of any following activity and not be delayed by any preceding activity • INDFj = Min ESk (k) – Max LFi (i) -Tj
A INDC = 20–16–2=2 B C D E 14 16 18 20 22 C’s Independent Float Time
Start Float and Finish Float • SFi = LSi – ESi • FNFi = LFi – EFi • Is there any difference between SF, FNF and Total Float?
Find A’s SF and FNF Lag = 4 Lag = 3
A’s SF and FNF SFA=0-0=0 FNFA=7-2=5 TFA=? Lag = 4 Lag = 3
So What’s the big deal about Float? • The CPM can give the project duration • The Critical Path has the longest duration • The planner gets some insights on the schedule • Can understand how much buffer each activity has • Can allocate scarce resources better • Also allows rescheduling activities while retaining dependencies