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Mae Angeline

Project Assumptions: How to Stop Them from Tripping You Up

Do your project assumptions leave your project vulnerable to set-backs? Yes, they can do...if they aren't managed. Let's walk through how to do just that.

Wouldn't it be great if you always had every piece of information you need for your project before you start? But in reality, that's not always the case. To get a project plan in place and start the ball rolling, you're bound to make a few assumptions along the way.

Some of these might be conscious and realistic – like the assumption that 90% of your team will be working during your project lifecycle, allowing for a few to be on PTO at any given time. And after your project starts, you can change and update your project's assumptions as more information becomes available.

But there are other assumptions that you might not be aware of. These are the ones that can land your project in trouble if they're proven wrong, because they're not even on your radar until it's too late.

Whichever type of assumption you're dealing with, the sooner you work out what they are, the more control you have over the course of your project. In this article, we will guide you through how to identify assumptions, what kind of effect they can have on your project, and how you can effectively manage them.

What are project assumptions?

A project assumption, as defined by the Project Management Institute (PMI), is a factor in the project planning process that is "considered to be true, real, or certain, without proof or demonstration."

Often these assumptions look and feel like common-sense. For example, you might reasonably assume that the project stakeholders will be available for meetings when they said they will be available (...however, you can probably already see how this assumption isn't a guarantee!).

Project assumptions can sometimes be traced back to projects you previously managed, or may be based on the data and information you have on hand. In this case, your assumptions will be based on the fact that you thought that this information was accurate - and perhaps it was at the time. But circumstances can change.

Truthfully, some assumptions do stem from wishful thinking. So, it's important to do your due diligence and identify where project assumptions create a vulnerability in your project plan - and to mitigate for those potential risks.

Why do we make assumptions in project management?

Human beings are faced with thousands of tiny choices and inputs every single day. If we had to second-guess our assumptions about every single thing, we'd be completely overwhelmed and we wouldn't get anything done.

It's a similar story in project management. The project manager has to make some assumptions in order for the project to proceed at all.

It's extremely unlikely, for instance, that the entire project team will storm out and quit all at once. Unlikely, but not totally impossible. However, it would be ridiculous to spend your time coming up with a contingency plan for this highly unlikely eventuality. Instead, you move forward with the reasonable assumption that it won't happen.

Some of these assumptions are so straightforward and "invisible" that they might not even occur to you. You assume that software updates will happen on time and without a hitch, for example, or that equipment will work perfectly whenever you need it, or that your office space rental will be renewed as usual.

There will also be calculated assumptions you'll make to get the project work moving. There may be uncertainties in the project planning, and questions without answers may appear. The project manager and team must fill these gaps with project assumptions for the work to move forward.

Because assumptions are, by definition, unfounded, all project assumptions carry potential risks. The project's outcome can be strongly affected if it turns out the project assumptions are off-base. Recognizing which ones are the highest risk, and regularly checking if they are still valid, will minimize the potential damage they can cause. It will also help you plan all the resources you will need for contingencies, in case the assumptions are incorrect.

How are project assumptions different from...

Project constraints?

Project constraints refer to any limiting factors that will affect how the project is carried out. Budgets and deadlines are typically the most significant constraining factors.

Project constraints are different from project assumptions because they're a known – if limited – quantity. However, there is a close relationship between assumptions and constraints, because assumptions often cause or exacerbate constraints.

Suppose you base your resource allocation on the assumption that all project team members will be available during the implementation of the project. If that assumption is proved wrong, you may face resource constraints as you try to complete the project with fewer human resources.

Conversely, possible assumptions related to areas of your project that are less constrained (or have a greater margin of error) will pose a lower risk to the project overall. If your scheduled timeline is very flexible, for example, then an assumption about the availability of a specialist for a critical task is less likely to threaten your project success: you have space to adjust your timings.

A contingency plan like this helps manage possible constraints that you may face due to project assumptions.

Project risks?

Project management is full of unexpected events, not all of them in your favor. Maybe you're faced with clients who keep changing their minds, staff emergencies, or supply chain issues. On the other hand, there may also be good circumstances like early approval of a project deliverable that can speed up the project schedule.

Whether positive or negative, an unexpected event in the project life cycle is considered a project risk. It can come in the form of a scope, schedule, technology, or resource risk, and can put the realization of your project objectives in danger.

Project assumptions, unlike risks, are "potential exposures" because you believe these conditions are necessary for the realization of the objectives of your project without proof or validation. When project assumptions turn out to be wrong, they can become a project risk that must be contained and mitigated.

Risks and assumptions play essential roles in project management, and you can analyze them to prepare for unexpected events. Identifying them may be a tedious and time-consuming activity, but being able to acknowledge them in the early parts of the project timeline is a good starting point for keeping your project on track.

Project dependencies?

While a project certainly depends on its assumptions, that's not to say that project assumptions are project dependencies. Dependencies, in project management terms, are other projects, tasks, or activities that need to be completed before parts of your project can begin.

However, dependencies create additional assumptions for your project, particularly when it comes to the project's timeline and expected budget. For example, suppose your website needs an upgrade to match your current marketing strategies. The completion of your marketing project is dependent on the website upgrade, and the upgrade needs to happen before you'll see a boost in your sales.

The assumptions you've made about this dependent task will have a significant impact on your project outcomes. The marketing project is now dependent on the web designer, and on the assumption that they'll be available when they said they will. If it turns out they're busy with another project and are delayed in starting work for you, then not only will your website upgrade be delayed, but your overall marketing output will also be delayed.

When managing assumptions, it's important to identify dependencies and take into account any assumptions you're making about the other, potentially conflicting projects that your team is working on.

Examples of project assumptions

Categorizing assumptions is a useful way to check in on your project. By considering different types of assumptions, it's easier to work out if there are hidden assumptions in your project plans.

Resource assumptions

Resource assumptions relate to the resources you need for the project. Examples of resource assumptions are:

  • The employees involved are readily available and open to working on all tasks.
  • Customers or clients will be available to answer questions or approve drafts when you need them to.
  • Materials and other supplies are all in stock within the project duration.
  • Both facilities and equipment are easily accessible to employees and clients whenever needed.

Budget assumptions

Budget assumptions are almost always risky, because of the limited nature of project funds. Assumptions concerning the budget may include:

  • Indirect costs will not go over the budget.
  • Funding stakeholders offer sufficient financial support throughout the project.
  • Fixed and variable costs will remain subject to a predictable rate of annual inflation.
  • Billable rates will remain the same for the entirety of the project.
  • For overseas clients, the conversion rate for currencies will remain stable.

Environmental assumptions

External conditions can also have an impact on the progress of the project. For example, environmental assumptions may have something to do with the technology, location or site, infrastructure, and even the physical, socio-economic, or political climate.

Here are some examples:

  • Technological enhancements will be compatible with the existing engineering or architectural framework.
  • The clients' perception of specific issues (like health) will be favorable to your product or service.
  • Amenities on the site will cater to all stakeholders, no matter their demographic type.

Time-based assumptions

Project factors that are related to time can be the most challenging parts of project management, and that's also true when we're dealing with assumptions. Time-based assumptions can have the greatest impact on production and delivery.

Time-based assumptions in your project might look like:

  • All employees will follow schedules for task completion.
  • The project will follow the set timeline and milestones.
  • Dependencies such as securing permission and approvals will not delay the production of deliverables.

How can project managers manage assumptions?

Keeping your assumptions under control and ensuring they are valid throughout the project is one of the key tasks of a project manager. Here are some ways to help monitor and track assumptions.

Start with as few assumptions as possible

This might sound obvious, but the more estimates and "best guesses" involved in your project plan, the greater the risk of your project being derailed by inaccurate assumptions. Take the time to make your work breakdown structure as detailed as possible, so there are no hidden surprises.

When creating a budget baseline, you may have used top-down estimating during the early stages of your planning, which relies on the similarities between your current project and a previous project you completed. Revisit this early in the project implementation stage and ensure every item in your work breakdown structure is adequately represented in the budget.

Create a complete assumption analysis

An assumption analysis is a project management technique employed by the team members to ensure assumptions constructed only have minimal potential risk.

First, all the people involved meet for a brainstorming session during the planning process, to identify the assumptions they're relying on. For each assumption that's identified, a risk analysis is performed to estimate the chances of the assumption being false, and the potential impact it would have on the project.

Some assumptions will be considered low risk (i.e. they're probably correct, and if they're not, the risk is low), but others will be higher risk and warrant a contingency plan.

Implementing an assumptions log

According to the Project Management Body of Knowledge (PMBOK), an assumptions log or project assumptions list is the documentation of all assumptions involved in project management. The assumption log records all assumptions, starting from the planning through to the actual project delivery.

Documenting assumptions in a single record helps centralize all information together in one place. When logging assumptions, you should include a brief description, the date it is logged, the owner of that assumption, and the plan to manage it, if applicable.

Establishing clear communication

Failure to communicate concerns about assumptions is one of the leading causes of project failure. In addition, it leads to a lack of transparency between the clients and the team, the leaders and members, and external stakeholders.

To prevent these issues, a proper review of initial project documents like the project charter and scope statement will help get everyone on the same page from the start. Check the validity of hidden assumptions in the project scope statement and the details of the resource costs, schedule, and range of your project.

Next, scrutinize the rest of your project plans to see if any assumptions will generate a risk, dependency, or constraint. Meet with your team to identify assumptions and develop plans to verify their accuracy or mitigate their potential impact. Finally, update the documents, and inform all key stakeholders of the changes made.

Use an effective project management tool

Project management tools with scope management features are an efficient way to monitor and keep track of project assumptions, and play an essential role in determining the accuracy of your plans. This will help you spot assumptions and adjust them before they have an impact on your resources, costs, and timeline.

A tool like Runn's scenario planning will allow you to plan and consider the "what ifs". Visualizing different events using real-time charts or tentative projects lets you peek at the wide variety of possibilities that might arise. You can check how the "what ifs" affect your team without changing your currently plotted plans.

Viewing scenarios in this way also allows you to predict what might happen with your human resources. It helps you take a step back to see the big picture of your resource capacity, utilization, and availability. You can customize the result by filtering any project inclusions and exclusions in the People Planner.


It's part of our human nature to make assumptions – and that's not always a bad thing. But as a project manager, you need to be aware of the assumptions you're making, so that you can consider and mitigate the risk they pose. The use of a reliable project management tool like Runn can help project managers identify, evaluate and communicate project assumptions effectively.

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