The Stacey Matrix: Agility or waterfall in the project?

Timo Gerhardt, Tuesday 10 October 2023 | Reading time: 11 min.

With the help of the Stacey Matrix, you can easily find out which project management method is appropriate in your project. For this, the project is categorized based on two dimensions.

How do agile and classic project management methods differ?

Projects are defined by the fact that they are always unique and complex in nature. Consequently, there is no one-size-fits-all approach to handling projects. A variety of common and less established methods exist. In principle, project management methods can be roughly divided into two groups: There are both agile and classic approaches.

Although agility is on everyone's lips these days and has many advantages, classic approaches also definitely have their raison d'être. Which type of method is appropriate in which case is highly dependent on the situation.

Agile approaches such as Scrum, the critical path method or Kanban are characterized by a fundamental idea of flexibility. Two essential aspects ensure that unparalleled adaptability can be guaranteed. On the one hand, a strictly incremental approach ensures that separate and fully functional units are completed during the development process, which are finally aggregated into a complete end product. On the other hand, iterativity refers to the implementation of feedback and repetition loops that ensure that an optimal result is successively approached. In a dynamic project environment characterized by uncertainty, this approach often comes into play.

On the other hand, there are the classic project management methods. Probably the most important and representative approach in this context is the waterfall model. This is characterized by a strictly linear process that manifests itself in a sequential project plan. This is processed linearly from start to finish until the project is finally completed.

The categorization of projects

In order to find the right method for your individual project, it is necessary to have a clear picture of it. The Stacey Matrix, created by British organizational theorist Ralph D. Stacey, helps to categorize projects in a goal-oriented way based on two dimensions.

The original matrix

Originally, the matrix did not deal specifically with project management. It was primarily intended to support decision-making in organizations. With this in mind, Stacey identified two relevant dimensions, which we explain below:

  • Agreement: The agreement dimension indicates the extent to which the stakeholders agree on a decision. In the best-case scenario, there is full agreement among the stakeholders. In the worst scenario it is possible that each stakeholder favors a different decision option. This disagreement represents a major challenge in decision-making.
  • Certainty: The second dimension indicates the degree of certainty with which decisions are made. Here, the decision-makers move along a spectrum from complete conviction to total cluelessness.

In the best case, there is full agreement and absolute certainty in the original matrix according to Stacey. In this case, the decision-maker's motto is: Just do it! After all, the rational and promising decision is obvious and waiting to be put into action.

The worst case, on the other hand, occurs when there is no consensus at all and total cluelessness about the outcome prevails. This is called chaos. In this case, it is necessary to act quickly and to continuously analyze and adjust the process. Further verbal exchange rarely leads to a better decision.

The realistic scenarios are probably mostly between these two extreme cases. If the agreement is high but the certainty is low, it is advisable to ask experts for advice. In this way, the uncertainty can be minimized. However, if certainty is relatively high but there is no agreement, then negotiations between the stakeholders will occur. If both certainty and agreement are only present to a relatively low degree, it is a complex decision-making environment. To optimize both dimensions and to create consensus and certainty, workshops or brainstorming sessions can be held, for example.

Thus, informed decisions can be made in an organization when dealing with complex issues. 

The Stacey Matrix in project management

The Stacey Matrix just described can be transferred to project management by making minor adjustments and holds important implications for the method to be used in the optimal case. The dimensions that are relevant for this context are as follows:

  • Requirement: The requirements for the project are the equivalent of the original Agreement dimension. Here, it is now a question of how clearly the requirements placed on the project or the steps to be carried out are formulated. In the optimum case, it is set out step by step how the project goal is to be achieved. On the other hand, however, the instructions can be completely vague and unclear.
  • Solution approach: The dimension of security becomes the solution approach in this context. If this is obvious, it is advantageous from the project team's point of view. However, it is suboptimal if it is completely unclear.

Five areas in the matrix now result from the characteristics of the two dimensions. If both the requirements and the solution approach are clear, the project is simple. If only the requirements are unclear and the solution approach is clear, the situation is politically complicated. This is the case, for example, when stakeholders disagree on the intended outcome. In the opposite case, we are again talking about a technically complicated project. Here, the planned result is clear, but the way to get there is not. If both dimensions are relatively unclear, the overall situation is rated as complex. If both the requirements and the solution approach are completely unclear, we speak of chaos.

The respective situations are visually represented in the following graphic:

The categorization of projects according to the Stacey-Matrix

Which method is the right one?

Categorizing projects using the customized Stacey matrix is helpful when it comes to determining the appropriate project management method.

If your project is simple, you are best advised to use a classic method, such as the waterfall model. After all, the requirements are clear, and the solution is obvious. All that remains is to draw up a corresponding sequential plan. Finally, this is to be worked through step by step. An example of this is the construction of a single-family home. 

A scenario in which the solution is clear, but the requirements are vague, is called politically complicated. In the opposite case, one speaks again of a technically complicated project. In both cases, certain difficulties prevail, but they can be eliminated through negotiations on the one hand, and through expertise and in-depth know-how on the other. Due to the existing ambiguities, strictly sequential planning as in the case of simple projects cannot be implemented. For complicated projects, agile methods such as Lean Management or Kanban are usually used. An example of this is hardly standardized construction projects, such as the construction of a large-scale highway bridge.

While complicated projects still exhibit a manageable degree of uncertainty, complex projects are characterized by it. Great difficulties arise in defining the concrete requirements, but also in identifying a suitable solution approach. Thus, the implementation of agile elements becomes even more important and aspects such as iterations, checkpoints, creativity and transparency are indispensable. After all, both the requirements and the solution approaches can change in the course of the project. Such a flexible approach to projects is needed, for example, in the development of groundbreaking innovations such as complex AR tools. Scrum is particularly suitable for this purpose. The corresponding framework is very extensive in this case but offers significant added value.

Finally, if both the requirements and the solution approaches are completely unclear, we are talking about chaos. Here, maximum agility is required, as planning in advance is almost impossible. An example of this is catastrophe management. The project progress has to be realized in many short steps. Stakeholders have to be involved again and again. Short feedback loops and flexibility are the key to success. Methods that are used here are Design Thinking, Lean Startup or the Minimum Viable Product.


The Stacey Matrix is a helpful tool when it comes to evaluating projects in terms of their complexity. In this process, categorization takes place, on the basis of which we can derive the use of a specific project management method. A central advantage of the method is its universal applicability. Due to the blanket and broad approach, the matrix can be used in any industry, in any company and in any department.

Nevertheless, the matrix should not be used as an absolute decision criterion regarding the project management method. Finally, the complexity of the project is used as the only evaluation criterion. This plays a significant role without question, yet other factors such as the project environment should also be considered. Another point of criticism is also the lack of clearly defined fields. The boundaries between the categories are vague and the classification is based on a very subjective assessment. A project could thus be classified differently by different people, which ultimately reduces the informative value.

Nevertheless, the Stacey Matrix helps to create clarity in complex project situations. Use it as a tool for deciding on a project management method. Nevertheless, try to identify other relevant aspects and let them flow into your decision. Experience values can also help you find the right method for your project.

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