Time Scheduling

Question 1

what is the definition of time scheduling

Answer 1

Time scheduling is a collection of techniques used to develop and present schedules that show when work will be performed.

and

Scheduling is the process used to determine the overall project duration and when activities and events are planned to happen. This includes identification of activities and their logical dependencies, and estimation of activity durations, taking into account requirements and availability of resources.

Question 2

what are the 7 steps of the project planning process

Answer 2

1. defining the project scope through the use of a work breakdown structure
2. identify the activities required to create work packages then determine their logical sequence
3. estimating the durations of activities thereby allowing a schedule to be created
4. determining the resources required and their availability
5. estimating the cost of the resources allowing a cost budget to be created
6. throughout this process, other constraints must be taken into account such as risk, quality, procurement and HSE
7. this process will culminate in a baseline plan for the project being created. Note that the above steps are not sequential and multiple iterations of each step are likely to be required.

Question 3

what are Precedence Diagramming Method (PDM) or Activity-on-Node (AoN) networks diagramming.

Answer 3

This method represent the activities as boxes or nodes with relationships shown as the logic connections between the boxes.

Question 4

what are the 4 types of logical relationships

Answer 4

Finish-to-Start - Predecessor activity must finish before the successor activity can start (most common relationship)

Start-to-Start - Predecessor activity must start before the successor activity can start

Finish-Finish - Predecessor activity must finish before the successor activity can finish

Start-to-Finish Successor activity must start before the predecessor activity can finish (very rare)

Question 5

Network diagrams can be further enhanced through the addition of lags and leads to specific logical links - what are they

Answer 5

Lag: creates a defined delay in the relationship (represented by the inclusion of a ‘+’ sign accompanied by the required time delay). Lags can be used on all 4 relationships

Lead: indicates an overlap between two linked activities (represented by the inclusion of a ‘-’ sign accompanied by the required time overlap), they can only be used with Finish to Start activities

Question 6

how is a network diagram node depicted

Answer 6

ES   |  D  |   EF
------------------------
ID DESCRIPTION
-------------------------
   LS   |   TF   |  LF

ES = Earliest Start
D = Activity Duration
EF = Earliest Finish
LS = Latest Start
TF = Total Float
LF = Latest Finish

Question 7

what is the Forward Pass - left to right

Answer 7

this pass calculates the earliest possible start and finish times for each task

Forward Pass:
Early Finish = Early Start + Duration (ES + D)

Question 8

what is the Backward Pass

Answer 8

this pass calculates the latest possible start and finish dates which will complete the schedule on time

Backward Pass:
Late Start = Late Finish – Duration (LF – D)

Question 9

Where a successor task on the forward pass has two predecessors, which ‘EF’ must be chosen,

Answer 9

the latest ‘EF’ must be chosen, that is, the EF with the higher value.

Question 10

When a predecessor task on the backward pass has two successors which ‘LS’ value is used.

Answer 10

the smallest ‘LS’ value is used.

Question 11

what helps remember the predecessor / successor rule

Answer 11

To help you remember ‘Highest number forward, lowest number back’, think ‘Big steps forward, small steps back’.

Question 12

what are the 2 types of float generally considered

Answer 12

Total Float: The amount of time an activity can be delayed or extended without affecting the total project duration (end date).

Free Float: The amount of time an activity can be delayed or extended without delaying the start of the succeeding activity.

Question 13

how is total float calculated

Answer 13

Total Float:
If the activity has a simple Finish to Start dependencies with predecessors and succeeding activities, the following formulae may be used:
Total Float = Late Finish – Early Finish
(LF – EF)
= Late Start – Early Start
(LS – ES)

Question 14

how is free float calculated

Answer 14

Free Float:
Free Float = Early Start of next task – Early Finish of current task

Where a task has two successors the time difference between the tasks may be different; the free float (if any) will be the lower of the two numbers calculated.

Question 15

what is the definition of the Critical Path

Answer 15

Sequence of activities through a project network from start to finish, the sum of whose durations determines the overall project duration.

It is identified on a network diagram as the path with the least total float, but generally has zero total float.

the longest path through the network

the shortest possible planned project duration

Question 16

what are 5 reasons the critical path is important in projects

Answer 16

1. to concentrate attention on activities which, if delayed, will affect project duration
2. to identify ‘near or sub critical’ activities – those with very little float may require similar attention to critical path activities
3. to identify ‘bulk work’ activities – those with large float:
   - these can be used to smooth forecast resource usage
   - they help identify where resources can be switched between bulk and critical activities to maintain progress
4. the critical path can be aligned with key milestones which is useful when reporting progress
5. risks associated with critical path activities may have a higher impact (especially with respect to time).

Question 17

what is PERT (Programme Evaluation and Review Technique)

Answer 17

Rather than use a simple single point estimate for activity durations, a figure is derived using the three-point estimate technique2.

The three points are based on an Optimistic Duration (shortest time), a Pessimistic Duration (longest time) and a Most Likely Duration.

The latter is not necessarily the average of the longest and shortest durations.

Question 18

how is the PERT duration calculated

Answer 18

The PERT duration is calculated according to the following equation and represents a weighted average of the three points:

PERT Duration =
O + (4 x Most Likely) + P / 6

Note that three point estimating is also used, though in a slightly different manner, during Quantitative Risk Analysis (QRA) as part of Monte Carlo analysis to quantify the total risk exposure due to uncertainty on the project.

Question 19

what are 9 characteristics of a Gantt chart

Answer 19

1. a timeline showing project calendar
2. the bar length indicates duration
3. tasks are usually positioned at earliest start and finish dates showing any float at the end
4. it is shown with or without logic connections
5. the critical path is identified, typically in red
6. it is the most common representation of a project schedule
7. it can also show comparison of current plan to original plan (baseline)
8. it can be generated using software tools
9. it can be rolled up into summary tasks and can show milestones (key events, moments in time)

Question 20

when is a Gantt chart typically produced

Answer 20

once the network is understood and the critical path analysis has been completed.

It is important to remember when producing a Gantt chart that a Legend or Key should be added so that anyone reading it understands the different colours and shapes.

Question 21

what is the definition of project Milestones

Answer 21

Milestones are significant events in the project and are normally associated with the completion of a key deliverable.

Milestones are represented on Gantt charts as activities with zero duration and are generally placed at the end rather than at the beginning of phases (for example once deliverables have been created) since the emphasis is on what has been completed rather than what is to be started.

Question 22

what are 6 characteristics of milestones

Answer 22

1. they define key events in the project (typically completion of major deliverables, intermediate products or results)
2. they can act as motivating factors for the team and/or suppliers (reward and recognition may be tied to successful achievement)
3. they mark the key decision points in the project (and may be linked to a go / no-go decision)
4. they are good for progress monitoring (e.g. summary table showing baseline dates against forecast or better still, graphically through the use of a milestone chart)
5. they help avoid too much detail about low level activities (the focus is on what is to be achieved, not how)
6. they are frequently used to trigger payments to contractors and/or from customers and are also used to trigger management approval for funding for the forthcoming phase

Question 23

what is a milestone chart

Answer 23

A Milestone Chart summarises progress towards completion of the milestones in a project.

It is a very simple but effective method of showing progress to key stakeholders in a graphical and easy to understand way.

Question 24

what are the advantages of using Project Management Software

Answer 24

• Allow rapid scheduling to be undertaken
• Fast and effective reporting capability
• Ability to format and store data in different ways
• Ability to manage large numbers of activities
• Ability to plan, schedule and review large, complex projects
• Ease of resource scheduling – levelling and smoothing
• Data extraction to other application formats
• Integration of project data with other corporate data systems
• Ability to consider different ‘what-if’ situations
• Enterprise project planning and management ability
• Ability to store multiple copies of a project for reference and audit purposes

Question 25

what are the disadvantages of using Project Management Software

Answer 25

• May require specialist planner to use effectively
• Could provide inconsistent results, depending on the application
• Requires investment in maintenance of the software – annually or at least on a regular basis
• Not always cost effective to use – this depends on the size and complexity of the project
• Can produce illogical results when software alone is used to make decisions (e.g. automatic levelling functions)
• Software can lead to less personal interaction allowing problems to be missed or misinterpreted
• The software may not be suitable for all project management methods (e.g. Agile) or if an iterative approach is adopted
• Quality of the output depends on the quality of the data input
• Frustration due to inexperience and unfamiliarity with the tool

Question 26

what are 2 common responses for a situation where the project end date is unacceptable to certain stakeholders

Answer 26

Crashing the schedule: Crashing involves adding more resource to the project. Additional funding may or may not be available for this.

Fast-tracking: This involves performing tasks in parallel that you initially planned to undertake sequentially. Project managers must carefully consider any risks associated with this course of action.

A third option to de-scope the project may also be considered if the above two options are deemed to be unacceptable.

Question 27

what are 3 alternative time scheduling methods

Answer 27

1. Line-of-balance
2. Time
3. Time chainage

Question 28

what is the Line-of-balance scheduling method

Answer 28

this technique is often used on projects that deliver repetitive products.

For example, construction activities on a housing estate development.

The technique is useful in showing how teams move from product to product rather than the detail of individual activities.

Question 29

what is the Time scheduling method

Answer 29

this technique is used on Agile projects, typically software development projects. The project is divided into several discrete periods (time boxes) that generally have durations of between two and six weeks.

The work scope and priorities are changed in order to meet the fixed timescale.

• Relies on incremental, iterative development cycles to complete less-predictable projects.
• Is ideal for exploratory projects in which requirements need to be discovered and new technology tested.
• Focuses on active collaboration between the project team and customer representatives

Question 30

what is the Time Chainage scheduling method

Answer 30

this technique is used on linear projects such as roads, tunnels, pipelines and waterways that shows the timing of activities combined with the physical location of the work. As such it is also referred to as “time-location” scheduling.