Describe at Least Three Approaches to Estimating Time (Effort)

Introduction

In today's competitive environment, it is absolutely necessary to deliver products and result on time and within budget, and having a repeatable estimating process in place and the ability to accurately estimate the effort and time to complete the project’s activities can be the difference between success and failure for the project. Estimating is ability to think somewhat abstractly on given tasks and figure out with some degree of accuracy what the level of effort will be, and needs a certain level of experience and expertise which does not always ensure that you’ll give good estimates but at least you can learn to be a good estimator.

Estimating activity effort techniques

The estimated project duration is based on the sum of the estimated activities duration. In talking about the techniques that can be used for estimating the time or effort necessary to complete the project’s activities it is very important to understand what activity duration is and why it is so important, for the project, to estimate it.

Activity duration estimation

After defining the activities, determining the interdependencies between them and figuring out their resources the next step in project time management is to estimate their duration. Activity duration is the time between the start and finish of an activity and includes the actual amount of work spent working on an activity plus elapsed time. As we can see the “elapsed time” term allow us to make the differentiation between duration and effort which is the number of workdays or work hours required to complete the task. Estimating activity duration, one of the most challenging aspects of project planning and a key to later cost estimation, is the process to analyze each activity, estimate how long it will take and it will depend on the amount of work required within the activity, how many resources will be assigned to this activity, who those resources are, and when they are available. In other words will create and maintain realistic project schedules with resources assigned and hours tracked at the task level.

To create an estimate that is accurate it is more than just adding up the activity durations. We also have to consider several factors that could affect the schedule such as constraints, assumptions, available resources, knowledge, skills, number of resources, risks and many others.

Approaches to estimating activity time and effort

The project schedule depends on the duration estimates of activities. A lot of uncertainties are involved in the estimate but the good news is that a number of tools and techniques can be used in activity duration estimating. The question is what is the best technique to estimate project duration?

There are many different ways to come up with an estimate and the most common are the traditional such as analogy method, parametric method, bottom-up method, decomposition method, three-point method, reserve analyze or expert opinion method, to say some of them. On most projects, particular techniques are not easy applicable.

Non-traditional methods differ in their techniques but ultimately they rely on estimates to plan for and meet projected deadlines. We can talk about three different team based and expert estimation approaches: Wideband Delphi, Planning Poker and PERT.

Wideband Delphi

The Wideband Delphi estimation method is a consensus-based technique for estimating effort and derives from the Delphi method which was developed in 1948 at the RAND Corporation when a small team of experts was asked to anonymously generate individual estimates from a problem description and reach consensus on a final set of estimates through iteration. Barry Boehm and his colleagues from Rand Corporation modified the method in Wideband Delphi, which included more estimation team interaction by iterations, re-estimation and assumption discussions. In this approach, known as an estimate-talk-estimate technique, the experts meet for group discussions prior to and during the estimation. There is a coordinator or facilitator who supervises the process, explains the component to be estimated and brainstorms estimation assumptions with the group and collects estimates. Then the team members individually create lists of the tasks they believe necessary and estimate these tasks. The moderator plots the estimates on a board, but keeps the values anonymous.