I. Definition
Story points are a unit of measure for expressing an estimate of the overall effort that will be required to fully implement a product backlog item or any other piece of work.
When we estimate with story points, we assign a point value to each item. The raw values we assign are unimportant. What matters are the relative values. A story that is assigned a 2 should be twice as much as a story that is assigned a 1. It should also be two-thirds of a story that is estimated as 3 story points.
What Goes Into a Story Point
Because story points represent the effort to develop a story, a team’s estimate must include everything that can affect the effort. That could include:
- The amount of work to do
- The complexity of the work
- Any risk or uncertainty in doing the work
When estimating with story points, be sure to consider each of these factors.
II. Estimate or not
Advantages
- Estimate allows to predict when a substantial increment of value will be delivered
- Estimates help our stakeholders plan ahead. It is part of the value we provide.
- Estimates can de-risk scope of uncertain size and complexity
- Estimated work can be traded in and out of scope for other work of similar size. Without estimates, you can’t trade.
- Estimating a task brings value, because its process involves more details and understanding of the requirements.
Drawbacks
- Estimates can be inaccurate and set false expectations
- Estimation can be seen as commitment which could be use against yourself
- Estimation is time-consuming
III. Techniques
Poker Planning
A typical Planning Poker set has cards with the following numbers: � 1 2 3 5 8 13 20 40 100.
- Everybody has the same amount of cards
- They draw one of these card to measure the backlog item (previously presented by the PO)
- The lower and higher numbers explain there reason
- The process is repeated until the team agrees, then we pass on to the next card
When the number on the card is 20 or higher, it either needs to be broken down, or sent back to the Product owner for more explanation.
Poker planning is fairly democratic but can be rather time-consuming.
T-Shirt Size
Here you need a scale of “t-shirt size”: XS, S, M, L, XL, XXL.
- The scale is put on table horizontally, you need to have the backlog item written down
- The team starts with one item of the backlog and discuss where to put it on the scale
- They can ask for information to the product Owner
- Once the size has been decided, we can add the Story Points according to the size
| Size | T-Shirt Size | Suggested Story Points |
|---|---|---|
| Extra Small | XS | 1 |
| Small | S | 2 |
| Medium | M | 3 |
| Large | L | 5 |
| Extra Large | XL | 8 |
| Extra Extra Large | XXL | 13 |
Easily set up, different way of implementing it, less arguing on numbers.
One Point One card
This method consist of using one story point per backlog item.
- The prediction is based on the previous sprint, the team is more likely to finish the same amount of task than last time
- The velocity is calculated via the number of stories per sprint
This method is very simple. Sprint goal may be separated from business value and risky items won’t be identified through points.