Tools And Techniques For Estimating Activity Duration
in my previous articles, I have talked about some of the inputs that are required when it comes to estimating activity durations for projects. In this article, I will be looking at some of the tools and techniques for estimating activity duration for projects. Follow me as I will be looking at that in this article.
Now the techniques…
#1 Expert judgement
The first and the most important tool for estimating activity duration for the project remains expert judgement. When you have a project at hand, you can always ask Subject Matter Experts to advice you on how to go about the project. They can now advise you on what to do and how long it will take you to complete the project activities from the beginning to the end.
#2 Analogous estimating
Analogous estimating is a technique for estimating the duration or cost of an activity or a project using data from a similar activity or project. The analogous estimation uses parameters from a previous, similar project such as duration, budget, size, weight, complexity, as well as the basis for estimating the same parameter or measure for a future project.
When estimating durations, this technique relies on the actual duration of previous, similar projects as the basis for estimating the duration of the current project. It is a gross value estimating approach, sometimes adjusted for known differences in project complexity.
Analogous duration estimates are frequently used to estimate project duration when there is a limited amount of detailed information about the project.
Analogous estimating is generally less costly and less time-consuming than other techniques, but it is also less accurate. It can be applied to a total project or to segments of a projecting may be used in conjunction with other estimating methods. Analogous estimating is most reliable when the previous activities are similar in fact and not just in appearance, and the project team members preparing the estimates to have the needed expertise.
#3 Parametric estimating
Parametric estimating is an estimating technique in which an algorithm is used to calculate cost or duration based on historical data and project parameters. Parametric estimating uses a statistical relationship between historical data and other variables to calculate an estimate for activity parameters, such as cost, budget and duration.
Durations can be quantitatively determined by multiplying the quantity of work to be performed by the number of labour hours per unit of work. For example, the duration on a project is estimated by the number of drawings multiplied by the number of labour hour per drawing. Or in cable installation, the meters of cable multiplied by the number of labour hour per metre. If the assigned resource is capable of installing 25 metres of cable per hour, the duration required to install 1,000 metres is 40 hours.
This technique can produce higher levels of accuracy depending on the sophistication and underlying data built into the model. Parametric estimates can be applied to a total project or to segments of a project, in conjunction with other estimating methods.
#4 Three-point estimating
The accuracy of a single-point estimate may be improved by considering estimation uncertainty and risk using three-point estimates helps define an approximate range for an activity’s duration.
- Most likely: This estimate is based on the duration of the activity, given the resources likely to be assigned, their productivity, realistic expectations of availability for the activity, dependencies on other participants, and interruptions in the project.
- Optimistic: The activity duration based on analysis of the best-case scenario for the activity.
- Pessimistic: The duration based on the worst-case scenario for the activity.
One of the common formulary for it is triangular distribution:
Look at this example
Most likely= 6 days
Using the Beta version
Therefore the duration is likely to be 6 days.
#5 Bottom-Up Estimating
Bottom-up estimating is a method of estimating project duration or cost by aggregating the estimates of the lower-level components of the WBS. When an activity’s duration cannot be estimated with a reasonable degree of confidence, the work within the activity is decomposed into more details.
The detail durations are estimated. These estimates are then aggregated into a total quality for each of the activity’s duration. Activities may or may not have dependencies between them that can affect the application and use of resources.
If there are dependencies, this pattern of resource usage is reflected and documented in the estimated requirements of the activity.
#6 Data Analysis
Another way of estimating activity duration for the project is by analysing all the documents that you have at your disposal. You have to check the documents that have been submitted by various experts and contractors in order to have an idea of how long it will take to complete the task of the project. I will talk more about data analysis in my future articles.
#7 Decision making
Decision-making techniques that can be used included but are not limited to voting. One variation of the voting method that is often used in agile-based projects is called the fist of five.
In this technique, the project manager asks the team to show their level of support for a decision by holding up a closed fist(indicating no support. If a team member holds up fewer than three fingers, the team member is given the opportunity to discuss any objection with the team. The project manager continues the fist of five processes until the team achieves consensus.
The project team may hold meetings to estimate activity durations. When using an agile approach, it is necessary to conduct sprint or iteration planning meetings to discuss prioritized product backlog items or user stories and decide which of these items the team will commit to working on in the upcoming iteration.
The team breaks down user stories to low-level tasks, with estimates in hours, and then validates )that the estimate is achievable based on team capacity over the duration(iteration).
This meeting is usually held on the first day of the iteration and is attended by the product owner, the scrum team and the project manager. The outcome of the meeting includes an iteration backlog as well as assumptions, concerns, risks, dependencies, decisions and actions.
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