Estimating activity duration is one of the many tasks aspiring project managers need to learn in order to start a project. Estimating the project duration is not always a simple task because it requires a Project Manager to apply best practices and methodologies as well as some theory.
For a long-term project, estimating activity duration is a time-consuming process. Ideally, you should include the main project team in the time estimation process. To reach agreement on the milestone dates and delivery schedules, you should consult with the project team, which will work on the project to accomplish its goals, the project management team, and all the key stakeholders who have been identified. You can create a schedule for your project with milestones based on this timeframe.
Iterative estimation of activity duration can be done for a project phase or a product phase. It can be modified as work progresses and as new project activities are discovered. At first, you can sequence the activities in the network diagram to estimate your project. It can be further modified in accordance with the adjustments made to the project during execution, controlling and keeping track of the procedure.
This is a crucial methodology that provides you with an estimate of the entire duration. You can get a general idea of the estimated total duration based on information on similar previous projects. The Project Management Office or another project manager may be able to provide you with this information; you can use this template for your current project. Â.
Analogous estimation of the activity duration is less precise but less expensive and time-consuming than other methods. When you don’t have enough time to do a proper estimate and you have a deadline, you can frequently use this method. Since you don’t have to estimate the entire project, analogous estimating can be used for a portion of it. If the requirement or nature of the phase is very similar to the previously processed project, you can estimate the activity duration for that phase.
This method is more accurate in nature. It is founded on a statistical analysis of previous data and additional variables. For instance, if you are designing a construction project, you may already know how long an activity will take, such as cutting 1,000 stones will take eight hours. Finding current activity duration estimates and historical project data is worthwhile if your project is of a similar nature to one completed in the past.
This type of estimate is based on taking into account a variety of factors, including the allocation of resources, uncertainty, and the risk involved, such as best-case scenario-based and worst-case scenario-based estimation. The PERT (Program Evaluation and Review Technique) is where the three-point estimating concept first appeared. Through PERT, we generally estimate three types of duration:
Most Likely (M) is the most likely of these, while Optimistic (O) is the most likely, based on the best scenario-based analysis. The final one, Pessimistic (P), is based on an analysis of the worst-case scenario. Once you have these, you can calculate the anticipated duration using some very helpful formulas. They are as follows:
Reserve analysis is a type of contingency reserve. You can create contingency reserve timing by adding a certain percentage to the derived schedule of each activity after fixing a schedule for each level of the activity based on the activity attributes. It can be adjusted as work progresses, decreasing or increasing as necessary.
You can successfully manage a project that is completed on time and within your budget by estimating the length of a project or its various phases. Save time when estimating the duration of an activity by drawing on the lessons that your organization has already internalized. Consider enrolling in one of Simplilearn’s online project management training courses, such as the PMP Certification, to learn more about effectively managing projects of all kinds.
Importance of activity duration estimates
Project managers can prepare for the time commitment of a project thanks to activity duration estimates, which are very helpful in project planning. Here are some other ways they are important:
What are activity duration estimates?
Estimates of activity duration provide an approximate time frame for a project task. They typically refer to work or business periods and can take the form of various time frames, such as hours, days, weeks, or months. A project manager can create a detailed project schedule and make educated guesses about the overall project timeline by estimating the length of specific activities. They can even use it to forecast project costs and communicate project objectives to stakeholders.
Project managers typically research the scope of the project, the characteristics of its individual activities, the resources available to complete the work, and historical data from previous projects in order to make activity duration estimates. The availability of team members and their skill levels often determines how long project activities last. Additionally, project managers can base their estimates of activity duration on their own expert judgments or those of other subject-matter experts. Each method for estimating activity durations can have its own benefits and dependability.
Activity duration estimate techniques
The outcomes and levels of reliability of project managers’ activity duration estimates can vary depending on the method they employ. Depending on where they are in the project process and how much work they want to put into making an estimate, a project manager can also decide which technique to employ. For instance, a project manager could estimate activity duration based on their own experience if they don’t want to perform calculations.
It’s a good idea for a project manager to create a “basis of estimates,” a document that displays the final estimate value along with the method used to create it, the method’s benefits and limitations, and the estimate’s accuracy. They can distribute this document to their managers, team members, and other interested parties. Additionally, although they may begin the project with a rough estimate, they are free to adjust it as the project progresses.
Here are some activity duration estimate techniques:
Analogous estimating
Project managers use the comparable estimating technique and base their projections on historical data, such as the durations of earlier projects with a similar scope. To estimate how long the current activities will take, they “analyze” or compare the current situation to these earlier observations. Depending on various factors, such as whether the project is larger, requires specialized products, or how much experience the team members have, they may adjust their estimate. For instance, if a piece of equipment malfunctioned and caused a delay in a previous project, the project manager may need to account for this in their calculations.
Parametric estimating
Project managers use statistical calculations to inform their estimates when performing parametric estimating. They extrapolate a duration estimate based on the values of work time per unit in previous projects and base their forecast on a trend. For instance, if constructing one wall previously took three days, a project manager might estimate that constructing three walls will take nine days. Alternatively, if a team needs an hour to paint one wall, it might take them ten hours to paint ten walls.
Expert judgment
The process of getting a duration estimate for an activity from a subject-matter expert is known as the expert judgment technique. Technical and subject matter experts with years of experience in a particular field or project managers who have completed similar projects in the past may be able to make an accurate prediction for how long a specific activity will take. Project managers can also combine expert judgment with other methods to improve an estimate’s thoroughness and accuracy. This method can be easy to use because it doesn’t involve any calculations.
Group decision-making
A project manager can consult their team to reach a decision about an activity duration estimate in a manner similar to the expert judgment method. By including the project team in the estimation process, the project manager may be able to make an educated guess based on more data and viewpoints, potentially increasing the accuracy of the estimate. It can also promote teamwork and make it possible for everyone on the team to concur on things like milestone dates and delivery schedules. This can ultimately increase work efficiency in a project.
Three-point estimating
Project managers create three data points using the three-point estimating technique: optimistic, pessimistic, and most likely A project manager can use a different method to estimate a realistic project duration, which is “most likely.” “Pessimistic” refers to the worst-case scenario, while “optimistic” refers to the ideal duration. These represent upper and lower bounds that an activity is unlikely to go beyond absent a serious, unforeseen circumstance. The project manager can then use a triangular or PERT/Beta distribution method to turn these figures into a final estimate.
Here is the formula for a triangular calculation:
E = (O + M + P) / 3
E stands for expected duration estimate, O for optimistic duration estimate, M for most likely duration estimate, and P for pessimistic duration estimate in this formula.
Here is the formula for the PERT/Beta distribution method:
E = (O + 4M + P) / 6
Through this procedure, a weighted address is created, which is marginally more precise than an ordinary average.
Bottom-up estimating
In bottom-up estimating, a project manager calculates the total duration of all the smaller project activities and adds them together. For instance, the final activity duration estimate could be 30 hours if a project activity has three distinct procedures, each of which takes 10 hours. Although this procedure can take some time, it can help project managers fully comprehend their estimate. Additionally, if necessary, it can let them change certain activity components to boost productivity.
Estimate Activity Durations process of Schedule Management
FAQ
How would you estimate activity duration in your project?
The PERT (Program Evaluation and Review Technique) is the most popular statistical tool for determining a project’s duration under the three-point estimates procedures. The PERT technique in project management is the most effective method for calculating an estimated project’s activity durations.
How do you calculate estimated duration?
In order to use the Three-Point-Estimating technique, three different duration estimates must be calculated: an optimistic, pessimistic, and a ‘most likely’ estimate.
Why is it important to have accurate duration estimates for activities?
For instance, the time required would be (80 / 1 / 8) = 10 days if an activity was estimated to take 80 hours and only one person was assigned and worked eight hours per day. Similarly, if four individuals were given full-time assignments, the duration would be (80 / 4 / 8) = 2. 5 days.
