Critical Path Description and Analysis
Have you ever wondered about how are projects that people would consider to be very complicated and time-consuming organized?
There are things in this world that you can’t just jump into without making a really thorough and detailed plan.
Some things can actually take time, effort and coordination, sometimes between a big number of people.
All that makes us think that managing a project is a really complicated task, and it is.
Luckily, there are ways and methods that can be used in order to make everything way easier, like CPA – or Critical Path Analysis.
WHAT IS THE CRITICAL PATH ANALYSIS?
The Critical Path Analysis, also known as the Critical Path Method, or shortened to CPA and CPM respectively, is a method used to set up an array of actions that lead to finishing a project.
This method is extremely popular and used in various settings because it’s such a great tool for managing projects.
The CPA is based on an algorithm that runs network analysis in order to serve project managers in dealing with complicated and time-sensitive procedures.
By definition, Critical Path Analysis is a method that calls for calculating every crucial task that is needed to complete a project.
The end result of the critical path is established by determining all the tasks that make up the project, their order and mutual dependency and the longest amount of time that is needed for accomplishing each of those activities that are a part of the path from the beginning until the end.
In addition to this, the Critical Path is also ordinarily used along with the Program Evaluation and Review Technique, or PERT for short.
Both of these tools make for a really powerful alliance.
THE HISTORY OF THE CRITICAL PATH ANALYSIS
The first time in history that we can find mentions of the term Critical Path Method (CPM) is in the late 1950s.
This is described as the period when the Critical Path is developed and when it was used for the first time.
First and foremost, it was developed by Morgan R. Walker of DuPont and James E. Kelley Jr. of Remington Rand.
In 1989 Walker and Kelley published a book by the name of The Origins of CPM: a Personal History, in which they write about their memories regarding the development of the method and the impact it created.
Around the same time when the CPM was developed, the U.S. Navy and Booz Allen Hamilton also developed the Program Evaluation and Review Technique, already mentioned above, which is still commonly used along with the Critical Path Method.
The importance of this method can be seen in the fact that it was used in many big and well-known projects in order to make their results successful.
Like we already know, organizing is one of the most important parts of success.
Before it was considered fully developed the CPM had a predecessor between 1940 and 1943 when it was successfully used for the first time in order to help the Manhattan Project, also known as the project that was used to develop nuclear weapons.
That being said it’s also really important to note that the Critical Path is usually used in industries that are dedicated to highly complicated projects, such as defense mechanisms, construction of various objects, research projects, engineering, aerospace industries and development of products.
However, if you want to look at this from a more familiar perspective, you could see really simplified examples of this method in everyday life. Like for example, in marketing.
For example, any project that is made out of tasks that are dependent on each other can be organized by using the Critical Path Method.
That could be making food for a big amount of people. Tasks like shopping, preparing, cooking and finishing different parts of different meals are all dependent on each other, and we already organize them organically, because that’s just logical.
However, as mentioned above, the true Critical Path method is used in much more complicated and long-term projects.
The first time that this method was used in major construction was in 1966 during the building of the former World Trade Center Twin Towers in New York City.
The timeline of the usage of this method shows fast development, which leads to improvement.
That being said, the original CPM approach isn’t actually in use anymore, but the term itself is implemented to any approach that is used to analyze and schedule projects.
A More Detailed Look at the Elements of the Critical Path Method
This method is used to establish everything – it’s a base for the whole project.
The preparation, the schedule and resources are all fit into a path further established by the method.
All of these aspects are crucial when you’re managing a project, and the method helps you keep track of the accomplishments regarding the project goals.
The established timeline shows you whether the project is early, on time, or late and needs to be set back on track.
Most commonly, the end result of the CP method is shown as a Gantt Chart.
This chart can be made using Microsoft Project or any other MS Project alternative designed for projects of intermediate complexity, or just a simple Excel spreadsheet for those of low complexity.
The point is to help you make progress and test the plan for your project to make sure that it’s successful.
The Critical Method Path helps the project manager determine which tasks have to be completed in which time period in order to successfully finish the project before the given deadline.
Using this method, you can also identify the tasks that can be delayed without harming the rest of the process.
In addition to this, the CP method can also help you determine the minimum amount of time that you’ll need in order to complete all the tasks.
This method is flexible in the way that you can always make a new “path” for the tasks once you encounter some kind of obstacle or time-restraint.
HOW TO APPLY THE CRITICAL PATH METHOD
When companies are working on a project that involves more complex planning and decision-making, and also risk-taking and higher stakes, it’s really necessary to determine which tasks are a crucial part of the path towards accomplishment.
Of course, as the risk of failure increases with complexity, the complexity of the tasks and subtasks that are a part of the project also surges.
That’s why it’s important to identify the relationships between all those tasks in order to come up with the right path for the project.
To put it very simply, there are always tasks that need to be done, or at least started, before others can begin.
That being said, the basic technique of the Critical Path Method is to set up a model of the project that consists of the following:
- A list of all the tasks or activities that are needed to wrap up the project (this is usually assorted within something called a work breakdown structure)
- The time (duration of time) that is needed for each task to be accomplished
- The ways that the task are dependent on each other and,
- Crucial factors and end results like milestones or important dates when certain tasks have to be finished
With all of these factors in mind, the Critical Path Method comes up with the lengthiest path of tasks needed to reach the endpoints or to finish the project, and the first and the last moments when tasks can be started or finished in order to meet the deadline and not prolongate the project.
By using this method, we find out which tasks are considered to be important or “critical” (on the lengthiest path) and which one of them are not as important or “total float”.
If a task is considered to be a “total float” it means that it’s important for the overall result of the project, but that it can be delayed or rescheduled without affecting the length of time needed to finish the project.
When a project is managed, a critical path is described as an array of activities that lead up to the longest path duration, not considering whether that path duration has or doesn’t have “float”.
This also helps the project managers determine which path is the shortest path needed to complete a project.
However, sometimes “total floats” are very much needed in projects.
For example, maybe a certain task has to be done at a certain time, or a certain place, or it just happens that some important resources are missing and they have to be acquired.
All of these things take time away from the projects and make them longer, but they are considered a part of the total float.
If we already make the total float a part of the path, or to make it simple if we already count in all the extra time needed for tasks, we won’t actually elongate the project path as we will have time to reschedule or delay tasks so that they suit us.
It’s important to note that not all tasks have to be “total float”.
Another way to differentiate the tasks is to assign them as either parallel tasks or sequential tasks. Sequential tasks are the ones that have to be done in a certain order.
Sometimes this means that a task has to be completely done in order to start the next one, but tasks can also be partially done.
On the other hand, parallel tasks are considered to be non-dependent, and they signify tasks that can be done at any time during the stages of the plan, before or after them, without consequences regarding the outcome.
As has been noted, some projects can be so complex that they require more complicated project paths. Some of them might even have to have a number of parallel critical paths.
That being said, even if a project consists out of multiple paths, there’s still a kind of a hierarchy between them.
If there’s another parallel path in the project, but it has a shorter duration or fewer tasks than the other path, it’s labeled as a sub-critical or a non-critical path.
Tasks on this path don’t have critical path drag, and they don’t elongate the time needed for the finalization of the project.
The tools used for the Critical Path Method can show us the deadline of the project and the tasks and the duration of the tasks that build up to it.
HOW TO DRAW A CRITICAL PATH ANALYSIS CHART
If you want to draw a Critical Path Analysis chart, you should follow these steps:
Step 1: Define All the Tasks that Make up the Project
Once you do this, it’s also important to define the earliest possible date to begin the task, the approximate amount of time needed to finish them, and whether the task is parallel or sequential.
If a task is sequential, you have to establish which of the other task that one is dependent on.
This way, you will be able to recognize the paths and patterns in which a project has to be done.
This can be easy to do in the form of a table.
The example shown here is very simple. Let’s say that you have a project and that you established that it consists out of 6 tasks.
|A||Starting task||1 week|
|B||Begin when A finished||5 days|
|C||Begin when A finished||5 days|
|D||Begin when B and C finished||3 days|
|E||Begin when D finished||2 days|
|F||Begin when E finished||4 days|
Step 2: Organize the Tasks in the Form of a Circle and Arrow Diagram
The Critical Path Method is often shown in the form of a circle and arrow diagram. In these diagrams, the circles stand for the particular tasks or activities, like for example the starting and finishing tasks. The circles are marked with corresponding task letters or numbers.
These marks are used to identify the tasks with ease. In some cases, you will find that the circles are also defined as nodes.
The arrows between the circles in these diagrams show the path of the task and what is needed to accomplish it.
The description is usually written on the bottom side of the arrow, while the expected duration of the task is written on top.
It’s also usual that the arrows go from left to right.
Just like circles can be called nodes, arrows are also sometimes known as arcs.
Here’s an example of a very simple diagram:
In the diagram given as an example, we can see that starting point (circle A), and the end result (circle B) are connected by an arrow which shows the description (below the arrow) and the duration (above the arrow/1 week) of the event at hand.
However, in the table given above as an example of the project, we can see the case when not one, but two activities can’t begin if the first activity hasn’t been completed. Diagrams like this tend to branch out in different directions, but still meet at the endpoint.
If you want a better explanation of these diagrams, check out this video:
For example, the EST for both tasks B and C is 1 week, because that’s how much time we need to finish up task A. But in order to calculate the EST for task D we have to add the amount of time needed to finish tasks B and C onto that one week.
Because both task B and task C can be done kind of independently at the same time, and both take 5 days to accomplish, we can just add those 5 days onto that one week.
That would mean that the EST for task D is now 12 days or 1.7 weeks.
You can add these estimated starting times to the diagram by writing them down in the upper right quadrant of the circle. The timing of the events can be changeable.
Another important thing is calculating the LFTs, or better known as the latest finishing time.
These signify the latest time that an activity can be done and are dependent on the established deadline.
Once you determine the LFT of a task, you can write it down in the bottom right quadrant of the circle to keep track of the timeline.
Important things to note about these diagrams are the following:
- Each task is labeled by either letter or number for easier understanding
- Tasks are not drawn to scale. Each circle and each arrow are the same size and length
- The starting time (written in the upper right quadrant) is usually marked as 0
This critical path has to be followed in order to deliver the wanted results on time, and in case that doesn’t happen certain repercussions have to be taken in order to get the project back on track.
Critical Path Analysis is also often used in project dedicated industries, but there are ways to use it in manufacturing and such.
WHAT IS CRASH DURATION?
Sometimes we will have to finish a project way earlier than was anticipated, and way earlier than we thought was possible.
Crash duration is a term used to describe the absolutely shortest possible time period when a task needs to be scheduled or finished.
It’s usually used to reschedule the path of the project so as to fit the new deadline.
However, crash duration or crash action does have a price.
When you look at tasks from this point of view, you have to determine what’s important: cost, quality or time?
If you find out that quality and time are important to you, you might have to invest more than you initially thought to do so that you can finish the project on time.
For example, if you have to finish a task two times earlier than previously imagined, let’s say your timeline narrows from 8 weeks to 4 weeks, you might have to hire twice the amount of people that you already have to finish that task.
That, in turn, doubles the price of the project but can be good in terms of productivity and social facilitation.
In other examples, you can see that crash action can completely change the path of the project and change which tasks are listed ac parallel or sequential.
We highly recommend using software such as Microsoft Project to make your CPA charts.
There are also other programs that you could use.
Unfortunately, it’s often that a schedule generated by the critical path method wasn’t used precisely.
In addition to this, the whole method of calculating time and establishing deadlines is based on estimations.
That being said, humans usually make mistakes when it comes to time estimates, as it all boils down to their current interest. If we make one mistake at the beginning of the path, the whole end result will be different.
This is why it’s important to never blindly believe the estimated times and to take everything with a pinch of salt. You don’t want to ruin the whole project by overestimating yourself or your team.
However, if the estimated times are realistic, there’s no problem.
The Critical Path Method is made in such a way that changes won’t really affect it if it’s used properly.
Everything can be rescheduled or adjusted in a way that suits you.
PERT (PROGRAM EVALUATION AND REVIEW TECHNIQUE)
PERT is very similar to the Critical Path Analysis, but the view that it has on estimated times is a bit more doubtful.
In order to use it, you have to take in mind the estimated shortest time an activity will take, the most realistic amount of time, and the absolute longest time if a task takes more than what was expected at first. After that you use the formula below:
This helps us determine the actual most likely time that it will take to finish a task.
ANALYSIS OF THE METHOD
The most important pros and cons of this method can be summed up like this:
- Can potentially help you reduce risks and investments that you need to make
- Makes you think carefully about the project itself
- Helps you realize the important parts of the projects
- Helps you determine which tasks are “floats” and where you could transfer resources
- It contributes both to making decisions and planning the project path
- Provides you with a simple view of even the most complicated projects
- Connects well to planning, financing and budgeting
- The Critical Path Methods relies extremely on humans and their estimates – which can be very wrong
- Just because you have a CPA doesn’t mean that your project is going to successful – it takes way more than just a good plan to accomplish something
- Last-minute time changes might not really sit well with resources that you had in mind
- If there are too many activities, the diagrams might become too complicated, and you might have to break the activities down into sub-activities
- Each project is unique in its own way and calls for a different approach
In addition to the statement made previously, we can further argue that the CPA can make a really big difference when it comes to project planning and the sole existence of the plan might help the project come through.
By realizing which parts of the plan are important, we can focus on them more and improve them.
We hope that this explanation of the CPA makes sense to you and that you will find a good and successful way to use it!
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