Sizing 

This is to best represent a value scale.   

Absolute estimating is the practice of applying an hourly, finite estimate to each requirement.   

Agile estimating uses relative sizing to provide a realistic way for teams to forecast workin a less formal and absolute way. 

Estimation

Estimates help the project team to:   

• Identify the time & effort required to arrive at the project schedule  

• Identify the right number of people required to do the work  

• Arrive at the budget by rolling up the cost of all activities required to complete the work; and  

• Prioritize the work in conjunction with the value that will be delivered. 

The biggest challenge here is the pervasive accountability culture that corporations have regarding estimates, deeming that once an estimate is set it is final and people are held accountable to it. That is exactly like telling your GPS that once it gives you an estimated time of arrival it must control the uncontrollable so that you reach the destination within the predicted time frame. One of the beautiful tenets of the agile movement is that storypoint estimates are not commitments but rather truly best effort estimates for future refinement. In other words, in a truly agile world, there are no heads in the sand. 

Some software developers fear to provide effort estimates as they are accountable to complete their work within the time.  Hence, they take so much time to get into the details to make sure they have enough information to provide the estimates.  Agile estimation helps to apply an estimate in a way that is conceptual and allows the team to view the work through a more relative lens so as nbot to get caught up on specifics and the belief that their estimate is tied to a definitive element like time or cost.  

The end result of an estimate is a concept of the effort required to do each work element, which can be translated into financial terms for project-feasibility determination and resource-allocation projections. 

Results show Absolute estimates should be used mostly to size small and simple tasks. This is actually a key principle we are told in school. Decompose complex and big problems into smaller and simpler ones so that we can see the big picture clearly. For this reason, relative estimates are the right answer to solving several planning problems in IT, such as initial estimates. Instead of detailing and decomposing an entire backlog without knowing all the necessary details for the vast majority of the items, it’s simpler to analyze the items by comparing them. 

The Management of Knowledge Work 

The traditional plan-based approach to work isn't flawed in and of itself; it just isn't suitable for managing knowledge work. In the task-work-based construction industry, the plan-based approach is suitable. The blueprints, which are the requirements, are fixed and probably won't change substantially while the building is being built. Therefore one can estimate how long it will take to build the steel pillars, pour the concrete, and so forth. The reason why the traditional plan-based approach is suitable for the construction industry but not a knowledge industry like the software industry comes back to the difference between the way we control the process of doing knowledge work versus the way we control the process of doing task work. 

 There are two major approaches to controlling any process: 

•  The defined process control model 

• The empirical process control model 

The defined process control model requires that every piece of work be completely understood. Given a well-defined set of inputs, the same outputs are generated every time. A defined process can be started and allowed to run until completion, and it will always produce the same results. The defined process control model provides and exercises control through planning, coordination, and control. The defined process control model is usually suitable when: 

•  No creativity or “new thought” is needed during execution; 

• There are mostly predictable actors that you can coordinate and control; and 

• It is possible to identify, define, schedule, and order all the detailed activities. 

 The empirical process control model provides and exercises control through frequent inspection and adaptation. The empirical process control model is usually suitable when: 

•  Creativity and “new thought” are needed during execution; 

• There are mostly unpredictable actors that you cannot coordinate or control; and 

• Execution cannot be planned in detail but rather by inspection and adaptation. 

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