Scheduling Flashcards

1
Q

what is the schedule

A
  • the project’s time plan
  • derived from the WBS
  • organises activities into their time sequence
  • takes account of dependencies
  • highlights critical activities and milestones
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2
Q

what is the process of scheduling?

A
  1. take activities defined in WBS
  2. estimate durations
  3. work out dependencies for each activity
  4. develop the network
  5. calculate total duration of project, critical path and float
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3
Q

what is a network?

A
  • visual representation of project
  • shows interdependencies
  • shows critical path
  • identifies float
  • AON convention (activity on node)
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4
Q

what is float

A

float - the about of time by which non-critical activities can be delayed without affecting the project’s completion date

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5
Q

critical path

A

those activities which, if delayed, would delay the whole project activities on the critical path have zero float

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6
Q

AON networks

A

activity on node network activities are shown as (boxes) nodes which are connected, showing dependencies using arrows

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7
Q

Draw node format

A
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8
Q

How do you calculate duration of project?

A
  • Forward pass through network
  • use earliest start time (EST) and earliest finish time (EFT) for each activity
  • EST is the same as the EFT for the preceding activity
  • EFT = EST +D
  • The Duration is the EFT of the final activity
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9
Q

How do you calculate float?

A
  • Backward pass through network
  • establishes latest start time (LST) and latest finish times (LFT) of each activity
  • LST = LFT-D
  • Float = LST- EST or LFT-EFT
  • LFT = LST of successor
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10
Q

How do you calculate total float?

A

difference between the LST for an activity and its EST
i.e. - on node either the difference between first top and bottom or last top and bottom number

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11
Q

what is free float?

A

the amount of time by which an activity can be delayed without affecting the earliest start time of any sucessor activity

free float = EST (of earliest successor) - EFT

free float is denoted at the top right hand side of each node pic

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12
Q

what is a gantt chart?

A

bar chart representation of the network
horizontal rows represent activities
task dependencies linked by arrows

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13
Q

advantages of gantt chart

A
  • resource histogram uses the same axis
  • easy to read overview of project
  • dependencies can be shown
  • progress-tracking can be used
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14
Q

disadvantages of gantt chart

A

dependencies not as apparent as in the network diagram can become confusing

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15
Q

What are lags?

A
  • time delay between activity ending and another starting.
  • e.g. paint left to dry before second coat
  • represented in network as a node labelled ‘lag’ and duration or on bar chart in the same way
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16
Q

what is crashing?

A

the reduction of the critical path, however there will be a cost associated with this.
(overtime labour, additional equipment)

schedule crashing considers the lowest cost option for reducing the critical path

17
Q

*How do you do crashing analysis?

A
  1. estimate cost of critical path activities at normal duration
  2. estimate cost of activities at reduced duration (crashed) - note that some activities cannot be crashed at all
  3. calculate incremental cost (per day/week saved) for each crashed activity - cost/time slope
  4. rank
  5. select a set of activities, at the lowest cost/time slope to be crashed
18
Q

What criteria would you use for re-seceduling activities?

A

Cannot re-schedule tasks on the critical path – as this will adversely impact the project completion date.
• Tasks with free float first, tasks can be moved within their free float without adversely affecting the EST of successor activities.
• Tasks with total float next, as these can be moved without affecting the project completion date.
• Consider which tasks would cause least disruption or difficulty to re-schedule, for example – go for small, easy tasks first.
• The context of the network as a whole, aim to met the resource requirements but whilst retaining as much float as possible within the network.