Understanding the Critical Path Method of Problem Solving

As project managers you can't do the second thing first if you want to find a viable solution, writes PMPlanet guest columnist John Jankowski of JanCom Technologies.


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Posted February 11, 2010

John Janowski

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Driving along the highway, suddenly a sharp, loud noise startles an unsuspecting driver. As the vehicle begins to grow increasingly uncooperative, it becomes apparent they likely have a flat tire.

So, what should the driver do next?

When asked, most people would respond “replace the tire.” Though they would be right in the general sense, the response ignores quite a few critical steps in the process such as safely pulling the car over, turning off the engine or even determining whether a flat tire is indeed the problem.

Just like any critical path method (CPM) plan for a project, a sequence of tasks emerges, though simple and largely intuitive, that must be performed in a specific order, one right after the other, to ensure a successful result. And so it is with many problems a project team is faced with on a daily basis. In essence, a critical path of steps must be taken to arrive at the proper solution to any given problem.

Any large scale IT project demands a very rigid, detailed means of solving problems. When JanCom Technologies is retained to consult for very complex IT infrastructure and data center projects, we rely upon dozens of experts who specialize in various subjects to solve problems that inevitably arise on every project. Asking general questions within such a diverse group of stakeholders will invariably result in answers that are as different as the people they are asked of.

Designing a data center, for instance, requires a variety of experts including the project’s architect and consultants, the general contractor and subcontractors, and the client’s own technology experts. Each of these parties have a stake in designing and delivering a state of the art data center, and each have their own perspective on how it should be done. To focus on problem resolution, I have adapted an analytical approach I call the critical path problem solving method. Like CPM scheduling, this approach effectively frames the issue and presents a clear path to resolution to all of the stakeholders. More importantly, however, this method also helps to efficiently arrive at a consensus solution.

Assessing the Problem

Though identifying and defining the problem would be self evident to many, it is also the most crucial step in the process. It sets the foundation for everything that follows. Returning to the example of a flat tire, there are a series of assessments that must be made to come to the proper solution. For instance, the driver needs to assess:

What is the extent of the damage? Can the problem be repaired on the road? Is the vehicle in a safe enough location to attempt a roadside repair? Is the spare tire in operable condition and does the driver have the necessary tools?

To answer any of these questions, the driver must get out and decipher what the vehicle’s issues really involve in order to assess the problem in more detail.

In many cases, when a specific issue or problem is inspected closely, more questions arise. For example, take the simple question: Can an end user install “X” number of servers in a particular row of cabinets? This question then yields a series of supporting questions such as is there adequate space, power or airflow? Although not exhaustive, these questions can help to produce an outline that can serve as a guide through the process.

critical path problem solving example

Though the example above is very simple, a critical path of questions does emerge. Answering question A.1 provides an avenue to answer B.1 and C.1, and answers to B.2 and C.2 are simply mathematical extensions of B.1 and C.1 and so on. This is a good example how a very linear process of answering relevant questions begins to provide a very clear path to what is reality is a complex project with many interrelated components.

If we were to act quickly in an attempt to address the first problem that presented itself and ignored the tangential issues, it could take significantly more time and resources to install a series of servers within an existing data center. In essence, the critical path method of problem solving defines the problem not simply by evaluating a singular problem as much as it defines an entire situation that impacts the final solution.

Identifying Questions and Constraints

Once the problem is properly defined, it may be necessary to then define not only the questions that must be answered, but also what constraints or limitations will be faced while working to solve the problem. By identifying the questions that need to be answered, the direction of the critical path becomes clearer. There are a number of techniques that can help identify the questions that need to be answered within the problem solving process.

A common method utilized by many project managers is the program evaluation and review technique, better known as a PERT chart. Typically used in the context of scheduling, in our case, this technique lists out the questions that must be answered throughout the problem solving process.

Smaller bubbles connected by lines that are either questions-with-dependencies(one must be answered to progress to the next) or stand-alone questions that diverge from the original path if they represent mutually exclusive questions―all of which lead to the eventual solution. This particular technique not only helps to organize any thoughts on the problem, it also provides a visual representation of the theory behind the critical path problem solving method.

PERT chart

No problem exists in a vacuum. There are always parameters that exist within a problem that not only affect the outcome, but also the way in which a problem can be solved. Two good examples that present themselves in most problems are money and time. For instance, the unfortunate driver of that vehicle with a flat tire may prefer to have a mechanic in a tow truck help them with their problem, but they may not have the money to pay for the service or the time to wait for them to arrive. As a result, the driver of the vehicle is forced to fix the flat tire themselves. Conversely, if the driver has neither the skills nor the required tools, then waiting for a professional may well be the most efficient solution.

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