Story Points explained - Part 3: Vs Other Estimation Methods
Story points are not the only way of estimating in Agile. There various other ways. Let's see how they compare to story point estimation.
Ideal Man Days
Ideal Man Days are just as they sound. Man Days. They answer the following question: If you were able to focus only on this task, with no interruption, how many days would it take you.
Ideal man days is easy for the team to understand as most teams and companies estimate in time. We can still clearly see the overhead our team goes through, if we use this estimation technique.
The biggest disadvantage of Ideal Man Days is that it couples estimations to team members. If one team member starts working on an Item and they get sick, another team mate needs to pick up where they left off. This will surely change the estimation on that item.
Story Point estimation does not have this problem as we estimate User Stories comparatively to each other.
T-Shirt Sizes
Similar to T-Shirt sizes we use XS, S, M, L, XL, XXL, XXXL, etc. The team compares User Stories with each other and puts them into their corresponding unit. You can do planning poker using T-Shirt Sizes. If you need to do a rough estimation of items, T-Shirt sizes are a great way to do it.
T-Shirt sizing is relatively easy to understand and to use.
One disadvantage of T-Shirt sizing is the fact that there are no numbers attached. In order to get velocity you can assign points to each size.
The Bucket System
It's great for estimating a large number of stories, but a big amount of people at the same time. The Buckets are set using the (modified) Fibonacci sequence: 1, 2, 3 , 5, 8, 13, 20, 40, 100, 200.
The Buckets are arranged sequentially. Pick a random card and place it at 8. The group can change this is they believe that the item is a different size.
Divide and Conquer is used as an approach. All remaining items are divided among participants. They can place cards where ever they feel they need to, without consensus of the other team mates.
A sanity check is done with all participants to make sure that there are no eyebrows raised.
Buckets are great to determine fast estimation in a very short amount of time.
The obvious disadvantage to Story point estimation w/ planning poker is that we are not using crowd wisdom to understand the details of the stories.
Large/Uncertain/Small
This is a rough simplification of the Bucket system, with only 3 sizes: Large, Small & Uncertain. Participants are asked to place the user stories in categories they belong to. The recommendation is to start with smaller User Stories and fill in Sall and Large. This leaves out Uncertain User Stories.
Affinity Mapping
A good technique when the team is small and no. of backlog items is less.
First step is Silent Relative Sizing: On a wall, a card with ‘Smaller’ written on it, is placed on the leftmost side and the card with ‘Larger’ written on it is placed on the rightmost side. Product Owner provides a subset of the items to all participants. All participants are asked to size each item relative to the sizes on the cards on the wall, considering the effort required to implement them. It is the solo decision of the participant without any discussion with the other team members. Product Owner or stakeholder is present to clarify the doubts of the participant. Product Backlog items which are too ambiguous to be understood by the team members for estimation are placed separately. It takes 5-20 minutes.
Editing of wall: The team members can change the location of the items on the wall. They can discuss design and implementation requirements with the other team members. This activity can be closed when little change is happening on the wall. It takes around 20-60 minutes.
Placing items in correct locations: After the discussions, the team places the product backlog items in their relative and appropriate positions. We can use T-shirt sizing, Fibonacci series etc. here to relatively estimate the size of the items.
Product Owner Challenge: The Product Owner may find some discrepancy in the estimations done by the team and need to discuss more features or the requirements for an item with the team. After discussions, final estimations are made.
Export to Project Backlog Management Tool: To make sure the information about the final estimations is not lost, export it to a product backlog management tool.
