Scheduling

Question 1

what is the schedule

Answer 1

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

Question 2

what is the process of scheduling?

Answer 2

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

Question 3

what is a network?

Answer 3

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

Question 4

what is float

Answer 4

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

Question 5

critical path

Answer 5

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

Question 6

AON networks

Answer 6

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

Question 7

Draw node format

Answer 7

Question 8

How do you calculate duration of project?

Answer 8

• 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

Question 9

How do you calculate float?

Answer 9

• 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

Question 10

How do you calculate total float?

Answer 10

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

Question 11

what is free float?

Answer 11

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

Question 12

what is a gantt chart?

Answer 12

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

Question 13

advantages of gantt chart

Answer 13

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

Question 14

disadvantages of gantt chart

Answer 14

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

Question 15

What are lags?

Answer 15

• 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

Question 16

what is crashing?

Answer 16

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

Question 17

*How do you do crashing analysis?

Answer 17

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

Question 18

What criteria would you use for re-seceduling activities?

Answer 18

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.