Project management lecture 3

What is a Gannt chart 

- type of bar chart that illustrates a project schedule 

- start and finish dates of all elements of the work breakdown structure are shown 

- dependency relationships between activities are also shown 

what does a netowork diagram show you 

- looks like a flow diagram

- shows timing information, which is needed by the project manager to manage the completion of the project as quickly as possible 

- it is more information per unit area of the chart 

network diagram 

explicitly defines and makes visible dependencies (precedence
relationships) between the WBS elements
• facilitates identification of the critical path and makes this visible
• facilitates identification of early start, late start, and slack for
each activity,
• potentially reduces project duration due to better understanding
of dependencies leading to improved overlapping of activities
and tasks where feasible

there are 2 common approaches = program evaluation and review technique (PERT)- US navy/ critical path method (CPM)- construction projects 

EET (earliest event time) 

earliest time any task can possible start/ finish based on timings of predecessor activities 

LET (latest event time)

the latest a task can possibly start/ finish without delaying project completion 

Network diagram formats 

- made from a series of nodes and connected arrows 

- 2 common formats = AoA (arrow to arrow) / AoN (activity on node)

- AoA = uses arrow to represent activities (tasks) and nodes to represent resulting events (deliverables) 

- AoN = node boxes represent activities and key project data 

layout of drawing a AoA diagram 

-arrow = activity that is being represented 

- top quadrant of node = EET 

- bottom quadrant of node = LET 

- at event 1, EET= 0 

- arrows leading in are the tasks/ activities needed to be complete for that event to occur 

EET calculation 

EET = proceeding EET + TE of connecting activity arrow 

- if there is one or more arrows going to the node, the EET would be largest total 

LET calculations 

preceding event LET - TE of connected acitivty  

-final LET = final event EET

-if there is one or more arrows going to the node, LET will be the smallest total 

-latest an event can occur without delaying project completion 

slack/ float 

a task has slack if its completion can be delayed 

2 types of slack 

- free slack = without delaying subsequent task completion 

- total slack = without delaying overall project completion 

slack calculation 

=LET - EET

-tasks that have a difference between LET and EET ( in the node diagram) has slack

 critical path 

sequence of project network activities which add up to the longest overall duration 

- Determines the shortest time possible to complete the project.( longest time to complete the project= shortest time for the whole thing)
– Contains all the tasks / activities with no slack
– A project can have several critical paths.

Any delay of an activity on the critical path directly impacts the planned project
completion date
• Other paths through the network with the total durations shorter than the critical path are called a sub-critical or non-critical path 

critical time 

total time to complete the critical path 

how can you shorten the project time

By shortening the critical path (in 3 ways):

- pruning critical path activities
– by "fast tracking" (i.e., performing more activities in parallel),
– by "crashing the critical path" (i.e., shortening the durations of critical path activities by increasing resources applied) 

crashing 

to crash a project or a task is to complete it in less time by deploying more resources to complete it 

-Careful planning is vital if we are to crash a project most efficiently  

(by deploying resources where they will make most difference)

- Crashing will almost always involve an increase in cost
- We need to know the cost per day of crashing a project
- Then we can judge the cost / benefit ratio and decide if and where to crash

crash cost per day calculation

(crash - normal)COST / (normal-crash)TIME