Originally, the Stacey Matrix was developed by Ralph Douglas Stacey as an aid to decision making. Today, it is no longer used in complex decision-making situations, but rather for selecting the appropriate project management method for a particular project. Not everyone agrees with this use and therefore the Stacey Matrix is viewed controversially.
Stacey dealt with many questions around decision making. He wanted to find out what factors influence complexity, how to make a good decision in an uncertain situation, and what strategies are suitable for making such a decision. The Stacey Matrix in the original is based on two dimensions: Certainty or certainty about the decision and the strength of agreement, i.e., how much do those involved in the decision agree. For each decision, the matrix examines how certain the decision makers are that it is the right decision and how many of them strongly agree with each other. In the Stacey Matrix, answers to these questions then appear in a graph bounded by the Certainty and Agreement axes. Different constellations then emerge from the points in the matrix: High Certainty and High Agreement means that the decision is easy. If everyone disagrees but is very certain about their opinion, negotiations are necessary. Here, it is quite possible that a final decision will have to be made from a political point of view. If everyone is in agreement but rather uncertain, Stacey advises refraining from strict plans and working out a common vision. Subsequently, step by step, work can then be done toward that vision. When there is neither certainty nor agreement, things get really difficult. Here, bad decisions are a high risk. A lot of creativity, innovation and flexibility are required. In extreme cases, the positions are so far apart and there is so little certainty that neither negotiations nor visions promise success. Here, another solution must be found.
With his matrix, Stacey wanted to bring order into the complex field of decision making. Recently, however, his matrix has been used by agile managers for something for which it was not necessarily intended, but where it can certainly help: Using the Stacey Matrix to determine which project management approach is the right one for a particular project. When the matrix is used in an agile environment, the labeling of its axes is often different from the original. Certainty is replaced by method or by technology. The question that needs to be answered is: Is it known which method leads to the goal? Agreement becomes requirements. Here the question is: How clear or unclear are the requirements? The result is again a similar picture to the original Stacey Matrix and the developers of this use of the matrix can deduce from the result which project management method is the most target-oriented.
The matrix is ultimately used to categorize projects into different gradations from simple to complicated. For simple projects, best practices are applied, known and proven methods are used, and unsurprising twists and turns are expected. Project managers here end up struggling "only" to stay on budget and on schedule, but the actual project process basically goes according to plan. Traditional methods such as the waterfall or V-method are suitable here.
In the case of complicated projects, which are still predictable to a certain extent, a distinction must be made between politically and technically complicated projects. Here again we find the phenomena that Stacey also elaborated. Either everyone agrees on the outcome but not on how to get there, or there is disagreement about why the project should be undertaken at all. Often, in such cases, many questions need to be answered, perhaps by consulting experts. In this type of project, approaches such as Lean and Kanban are usually used.
In highly complex projects, there are an enormous number of risks. Here it is hardly possible to create a plan and then follow it through to the end. In most cases, not even the target or the requirements for the result are sufficiently known. Here, particularly creative and flexible solutions are required. The project stages are flexible and the points in time at which everything is questioned and reviewed are often short, simply because so much is unclear. These highly uncertain and poorly assessable projects literally cry out for Scrum or other particularly agile methods.
Lastly, there is an area in the matrix called chaotic. This includes only projects that fall completely off the grid. In other words, there are virtually no requirements or methods. Traditional planning methods are ruled out from the outset. This is where the discussion is most heated and opinions differ: Is Kanban the best method or rather Scrum or Design Thinking? Each method has its advocates and since many of these chaotic projects fail, but others miraculously achieve a grandiose result, the discussion will not end anytime soon. Ideally, if you have a project that must be classified as chaotic, try to move it into the realm of the complex by gathering information and answering questions. If that's not possible, extra creativity, flexibility, and ingenuity are required.