Topic

User Story Estimating

Response

Agile teams use a relative sizing technique to estimate the effort required to complete a product backlog item. The relative technique is used for both Features and User Stories. Agile teams do not use man-hours or man-days to estimate effort. Agile teams use relative sizing based on using a crowd estimating technique to address the well-known issues associated with traditional project planning techniques.

The need to adopt a relative sizing techqniue is because humans are poor at detailed estimating.

And to reach any sort of level of confidence Teams created a staggering amount of information, which didn't always identify the most important.
In the majority of cases the overall estimate overlooked the effort needed to ensure an effective transition from one stage of the life cycle to another. For example, transitioning from design to construction or construction to testing.
These traditional techniques contained very few safeguards to ensure the information was interpreted in the way the author intended by everyone across the life cycle.
As requirements were implemented teams discovered additional effort was required leading to scope creep and delays.

Humans are really good at comparing the complexity of one thing against another.

for example, the complexity of producing a skateboard versus a bicycle,
- a car versus a bus,
- or a heavy goods van versus a helicopter
- When comparative estimating is performed as a team quickly converge on a common perspective through discussion

Agile Teams adopt different units to reduce confusion between Features and User Stories.

they use T-shirt sizes (ranging from extra extra Small to extra extra Large) for Features
they use a Fibonacci points scale for User Stories (for example, 0.5, 1, 2, 3, 5, 8, 13, 21)

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Additional information, including working examples and templates are available in the Monetical knowledge base.