Critical Path Analysis

Starter – The Big Breakfast! On Saturday, I want to cook myself a big breakfast.I want to have some toast, scrambled eggs and some bacon. It takes me 3 minutes to make the toast It takes 1 minute to break and whisk the eggs and then I need to put them in the microwave for a further 3 minutes. The grill takes 2 minutes to heat and bacon takes 4 minutes to cook under the grill. The breakfast takes me 1 minute to serve and a further 10 minutes to eat. Once I have eaten my breakfast I need to wash up which takes a further 2 minutes and then put the plates away which takes 2 minutes. What is the quickest time I can do this in?

1 Put the grill on 2 Put the bread in the toaster 3 Whisking the eggs takes 1 minute 4 Put the eggs in the microwave – need to be in for 3 minutes 4 Once the grill is ready I put the bacon in – total time so far is two minutes 5 The toast is ready after 3 minutes and the eggs are ready after a total of 4 minutes 6 The bacon finishes after 6 minutes – 6 minutes so far 7 The breakfast takes 1 minute to serve – 7 minutes so far 10 – It takes 10 minutes to eat – 17 minutes so far 11 – Washing up and putting away takes 4 minutes – 21 minutes Why is it simply not a case of adding up all the times to get a total?

Simple example

Planning and Monitoring Tool

Critical Path Analysis (CPA) Key term: A technique for planning complex projects to allow them to be completed in the shortest time possible by identifying activities that can be carried out simultaneously.

Advantages of CPA Helps reduce the risk and costs of complex tasks Should improve efficiency Encourages careful assessment of the requirements of each activity in a project Help spot which activities have some slack (float) A decision making tool – helps with other aspects of business planning (e.g. cashflow forecasting and budgeting)

Disadvantages of CPA Reliability of CPA depends on accurate estimations Limited usefulness on large, complex projects CPA does not guarantee the success of a project Too many activities may make the network diagram too complicated. Activities themselves may need to be broken down into mini-projects

The Process

CPA – the Process Identify and prioritise the activities Identify which activities MUST be done before others EST – identify earliest start time LFT – identify latest finish time Identify the FLOAT – tasks which can be completed outside the critical path Identify the critical path – points connecting ESTs and LFTs (where these are the same)

Critical Path Analysis Nodes: Show the start and finish of a task 12 Node numbers showing order of activities in the left hand semi-circle of each node. 3 Earliest Start Time (EST) 5 Latest Finish Time (LFT) A 3 B 5 Arrows indicate the order of the tasks, the letter above shows the order, the time period below the arrow The Critical Path

Nodes and activities EST LFT Activity paint wall 12 EST LFT Time 3 hrs The node shows the physical start and finish of an activity The arrow shows us the actual task which is being undertaken

Constructing the network 12 1 Start the project 2 The first job 3 Finish the job 4 Start the next activities

Building a network Complete tasks 3 &4 6 Start the next activity once both 3 & 4 are complete

The completed diagram 7 Finish the job Give each node a number

Adding the information a b c de f Add the activities and times 24 hrs 3 hrs7 hrs 3 hrs2 hrs 3 hrs

The earliest start times a b c de f Add the earliest start times hrs 3 hrs7 hrs 3 hrs2 hrs 3 hrs

The latest finishing times a b c de f Add the latest finishing times hrs 3 hrs7 hrs 3 hrs2 hrs 3 hrs

The critical path a b c de f hrs 3 hrs 7 hrs 3 hrs2 hrs 3 hrs * * ** Critical activities are a, b, c, f.

The float With the network complete, you can now identify any idle time. This spare time is known as the float. Resources can be allocated to other duties during the float time. In this activity there is only one critical time - between tasks d and e, where there are 5 floating hours. Float is calculated by: Float = LFT – (EST - Duration)

Good news!! You will not be required to complete a CPA diagram from scratch, you will be asked to complete some elements (ESTs and LFTs) of a partially-finished diagram

Plenary – CPA Revision Quiz ness-studies/comments/revision-quiz-critical- path-analysis ness-studies/comments/revision-quiz-critical- path-analysis