No.3 Flashcards
Network diagram one: activity on arrow
Activity on arrow is a network diagramming method in which activities are represented by arrows. The tail of the arrow represents the start and the head represents the finish of the activity (the length does not represent the expected duration of the activity). Activities are connected at points called nodes(drawn as circles) to illustrate the sequence in which the activities are to be performed
Network diagrams: activity on node
Activity in node is a network diagramming method in which activities are represented in boxes or nodes. Activities are linked by arrows tos his the sequence in which activities are to be performed.
Network definitions
Es = Earliest starting time Fs= earliest finishing time Ls = latest starting time LF = latest finishing time Ts= total slack (= ls-Es OR lf-ef Fs =free slack ( es-ef)
Total slack
Total slack is the amount of time an activity can be delayed without delaying the project
Free slack
Free slack is the amount of time an activity can be delayed without delaying the early start of any successor activity
Network diagram
No. Activity Dur
ES. Name. EF
LS. TS. FS. LF
CriticAl path definition
Critical path is the longest combination of dependant events through the project
Includes those activities that have no slack and if delayed will delay the project as a whole
Network diagram shortfalls
Network diagram shortfalls are
Difficult to visualise concurrent activities as no time axis is available
Resource usage is neglected (concurrent use of resources are ignored)
Time estimation
A time estimate is an estimation of the time under uncertainty
Three point estimation
Ave weighted = opt + peas + 4 ml all /6
Opt = most optimistic time estimate
Pess = most pessimistic time estimate
Ml =most likely time estimate
Time buffer calculation
A safe time estimate (prob of 90% that the actual time will fall within this estimate)
An aggressive time estimate (prob of 50% that the actual time will fall with this estimation)
For each activity calculate the difference between safe and aggressive time estimations
Sum the differences together for the activities on the critical path
Use a fraction of the summed difference as the time buffer for the project (aggregation)
Bar charts (gantt charts)
Simplest and most common way to present a project plan
Portrays work packages, tasks and activities as well as the status of the project visually against a time axis
Is developed from a WBS analysis
Progress estimation (50-50 rule)
Breakdown tasks in roughly the same sizes in terms of time
Apply the 50-50!47@3: 50% progress of activity is started and remaining 50% when completed
Resource loading
Resource loading describes the number of individual resources the existing schedule requires
Resource levelling
Resource levelling aims to minimise the period by period variations in resource loading using slack times, off loading and multi tasking
Work authorisation
Formalises agreement between people delegating work and those accepting responsibility to do the work (SLA)
Control process
The control process is the setting of a standard (objective or plan)
It determines facts about the actual situation and anticipating future deviations from the plan
Comparing the actual facts with the standard
Taking actions to bring the actual situation in line with the standard
Project control characteristics
Look ahead
Frequent monitoring
Balance quality cost and time
Contingencies
Earned value concept
The earned value concept is integrating cost reporting with progress reporting
It represents an estimate of the percentage of work completed thus far
Earned value definitions
Pv = planned value (budgeted cost of work scheduled) Ev = earned value (budgeted cost of work performed or supposed cost)
Ac = actual cost
Sv = schedule variance (Sv = ev -pv)
Tv = time variance (sp - status date)
Sp is the date where pv = ev in time units)
Cv = cost variance (cv = ev- ac)
Positive variance implies good result s
Schedule performance index SPI
SPI compares the earned value with the plan. Gives an indication of performance relative to the schedule. Spi = ev/pv
If SPI >1 it’s ahead of schedule
Cost performance index
CPI compares the earned value with the actual cost
Measurement of performance relative to the budget
CPI = EV/AC
CPI >1 cost saving
