One most common example of Relative Estimation is when ordering a Cold Drink in MacDonald you will not share the exact size of cold drink but you’ll order by mentioning Medium, Small and Large as Exact Size is not Important.
Planning Poker Story PointSimilarly when ordering Pizza you will not tell exact size of pizza rather you will tell Small, Medium, Large, Extra large Pizza as exact size is not Important.
This is T-Shirt or Bucket Size Estimation in terms of (X-Small, Small, Medium, Large, Extra-Large).
So similarly in Relative Estimation size is not that important but relative value of each other.
Using Story Points for Quick Estimation
Unit of Measure that express relative complexity.
It would be difficult to estimate size of Green Square but it’s easy to tell that Green Square is 4 times of second square – This is Relative Estimation (Green Square – 4 Points, as 1 Point is for Small (second square).
Compare the sizes of features to each other to determine a relative size (Refer Figure).
Its difficult to exactly measure predict distance between from Delhi to Bhopal, Delhi to Mumbai, or Delhi to Chennai. But if I say that the distance between Delhi and Bhopal is 1, then I can also mention below statements based on it:
- Delhi to Bhopal is 1.
- Delhi to Mumbai is 2.
- Delhi to Chennai is 3
So Delhi to Chennai route is roughly three times longer than the Delhi to Bhopal route. Similarly Delhi to Mumbai route is roughly two times longer than the Delhi to Bhopal Route.
As you can see in this example, our reference is route between Delhi and Bhopal.
We made it our “1” story point. If I replicate this exact exercise and substitute time.
As soon as you have your reference (or base) user story and if the reference user story is 1 Point, then does the next user story look the same? Bigger?
If it’s about the same, then you give it a 1. If it looks bigger, then you need to decide if it is twice as big (2 Story Points), three times bigger (3 Story Points), and so on.
As soon as you know the reference story and its point value, you will have all your subsequent user stories properly estimated in a much faster way than using time-based estimates.
It’s all about accuracy, not precision.
Story Points are estimates of effort and determined by the amount of work, complexity, risk and uncertainty.
Estimation should be based on everything – not just development
Unit of measure to estimate the required overall effort to implement a product backlog item
When we estimate with story points, we assign a point value to each item. The 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.