Estimate Activity Duration – 6 Tools
Professionals who seek to build a career as a project manager must learn how to create a complete and comprehensive project schedule. Basically a schedule is a list of projects deliverables, tasks and milestones with start and finish dates. Those are often estimated by the help of other information such as resource quantities, activity dependencies, budget and constraints. It is not always an easy task for a project manager to estimate the duration of activities because this requires knowledge and judment. There are some tools to be used for estimating activity duration while creating a work schedule. In this article we will discuss six tools :Analogous Estimating, Parametric Estimating, Three Point Estimates, Expert Judgement, Reserve analysis and Group Decision Making Techniques to estimate activity duration.
Estimate Activity Duration Process
Estimate Activity Durations is a process which is performed to estimate the work periods required to complete the tasks with estimated resources. This process provides the duration of each activity which is one of the most important inputs for a project schedule.
Inputs of the estimate activity duration process is as follows;
- Schedule Management Plan
- Activity List
- Activity Attributes
- Activity Resource Needs
- Resource Calendars
- Project Scope Statement
- Resource Breakdown Structure
- Risk Register
- Enterprise Environmental Factors
- Organizational Process Assets
These are the inputs of the estimate activity duration process. Using these inputs with the six tools, you can estimate the duration of each activity and update the project documents if needed.
6 Tools to Estimate Activity Duration
While preparing a project schedule it is critical to define the duration of each activity. Because overall project duration is associated with the durations of activities in the network system. If the durations of activities are not properly estimated, project completion date will be wrong and the critical path will not be realistic. There are six essential techniques widely used by the schedulers and planning engineers to estimate activity duration and crate the network system. These techniques are ;
1. Expert Judgment
2. Analogous Estimating
3. Parametric Estimating
4. Three Point Estimates
5. Reserve analysis
6. Group Decision Making Techniques
Now we will discuss each tool in detail.
Expert judgment means using experts who have knowledge of the related field and experience in estimating activity duration. Expert Judgment can be provided by a member or multiple members of the project management team.
Analogous estimating analyzes a similar project completed in the past and makes a round estimation for the current project by the use of this past projects datas. For instance, let’s say you have to estimate the duration of a hospital construction project with the help of the analogous estimating. In case you will use your previous hospital project’s datas such as task durations, milestones and their relationships.
Although this method enables to make duration calculations easily and quickly, estimations are not accurate enough.
Analogous estimation provides an entire duration estimation. You can perform this estimation when you have a limited time to make a proper estimation.
Parametric Estimation Technique can be considered as a consolidation of historical information and statical data. It is a definite technique to identify both cost and time for a current project using data from past projects with duplicate parameters. For instance, let’s say you have to build a dam and you measured some of the major task’s quantities. By using productivity rates of machines from the previous project, you can estimate your current project’s duration.
Parametric Estimation Technique provides more accurate estimation than analogous estimation.
Three Point Estimates
Three Point Estimating Technique is a usefull which helps to increase the accuracy of cost and time estimates. There are three parts of this technique which provide three different estimates.
• Most Likely Estimate:Assuming a normal case in which everything goes as usual.
• Pessimistic Estimate:Assuming everything goes wrong.
• Optimistic Estimate: Assuming everything goes as planned.
PERT (Program Evaluation and Review Technique) uses the three point estimates.
Reserve analysis can be considered as a contingency reserve. Once you fixed the schedule for each activity, you can add contingency reserve durations to each activity. These contingency reserve durations can be changed depending on the situation, they can be added as a percentage of the duration of each activity. Reserve analysis helps the project team to manage schedule risks to minimize their impacts.
Group Decision Making Techniques
Group decision making techniques can be used to estimate the duration of each activity. In this technique you consult your team members or experts to provide the best estimates for the schedule activities.
Estimate activity duration is an extensive process which requires various inputs and tools. Ideally, you should consult your team members while making estimations. You can get more realistic results if you involve your project team and encourage decision making. Because they are aware of the major project milestones, project deliverables and key stakeholders.
Estimate activity duration has an iterative nature which can be performed for both projects products. Estimates can be changed as the work progresses and new activities are added to the schedule.
Making accurate estimations can help you to manage your project schedule successfully. If the project schedule is created with realistic estimations, project resource and cost distribution will also be realistic.