Agile Estimation Techniques

Posted on by lakshaysuri

Agile Estimation Techniques are used to estimate work effort in agile projects. The commonly used techniques are

  • Planning Poker
  • T-shirt sizing
  • Dot Voting etc

Planning Poker

Planning Poker is used to assign a story point to a feature or item during the sprint planning. For agile estimation purposes, following values for estimating an item: 1, 2, 3, 5, 8, 13, 20, 40, 100. The process that happens during sprint planning:

  • Each team member gets a set of cards.
  • The Product Owner explains item to be estimated.
  • Each team member choses a card that represents his/her estimation.
  • Every one shows their respective card at the same time.
  • The point value shown on the card is the estimate if every team member selected the same card.
  • If the cards are not the same, then the team needs to discuss the item and estimate again.
  • Select again until estimates converge.
  • Repeat for each item.

Note:

Quick estimation can be done for instance

  • when few members estimate as 2 and few estimate as 3 then choose the bigger one.
  • If the different cards shown are like few with 2 and few with 8 then ONLY do the discussion.

T-shirt sizing

T shirt sizing estimation is a QUALITATIVE estimation technique and does not include QUANTITATIVE aspect for estimation. Normally this technique is used to estimate EPICS (and can be used for stories too) and it gives a rough estimation.

Where can T-shirt sizing be used?

We had a project to be finished in 2 months but none of us (Product Owner, Scrum Master, Developers) were sure if we could really finish it within 2 months. The only thing we had were the REQUIREMENTS defined in the backlog. Therefore we used this technique to quickly go through all the EPICS to come up to a fair estimation to decide if we could do the project or NOT.

How does T-shirt sizing technique work?

Here a requirement is classified as XS, S, M, L, XL. This means a requirement can be either extra small, small, medium, large or extra large.

  • Each team member gets a set of cards with XS, S, M, L, XL written over them.
  • The Product Owner explains item to be estimated.
  • Each team member choses a card that represents his/her estimation.
  • Every one shows their respective card at the same time.
  • The point value shown on the card is the estimate if every team member selected the same card.
  • Estimation should be done again for an item – if someone estimated XS whilst other one estimated as XL. If majority estimated M or L then go with an L.
  • Repeat until each item is estimated.
  • Once all the items have been estimated, a mapping from t-shirt sizing to the quantitative aspect should be done.

In our case we mapped it as

XS -> 3, S -> 5, M -> 8, L -> 13, XL -> 20.

This way team came up with number of story points needed to finish the project and based on our average sprint velocity we came up with how many sprint we would need to finish the project.

Dot Voting Technique

It is basically a ranking method to decide the order of the Product Backlog from the highest priority stories to lowest priority stories. It is done to select the most important story to be taken forward.

  • Product owner puts all the user stories on the wall using  post-its.
  • Team members are given 4 to 5 dots (mostly in the form of a marker)
  • Everyone has to give their votes on the different user stories that they prefer (keeping into account the max dots that are available with per person is fixed and should not be exceeded).
  • Product Owner then orders the product backlog items from the most preferred (one with most no of dots) to the least preferred (one with least no. of dots).
  • Discussion can be held if a team member is unhappy with a specific task having higher or lower priority.