Saturday, 3 October 2015

The Importance Of Estimating Requirements

The Importance Of Estimating Requirements 

I havent been blogging for a while mainly because Ive been doing some DIY work in my house, so although my blogging and my readers have suffered my kitchen is looking much better .
In this blog Id like to talk about Estimation, something developers dont like much.
Estimating requirements and estimating accurately is more important than most developers think it is. Most think it is just another administration task that stops them developing, but without it companies struggle to operate correctly.
There are different types of estimating such as using story points Or using estimating by time.
Personally I suggest it doesnt really matter which method you chose to estimate stories. Remember a story at this stage has the basic outline of the work and not the detail, so the estimate is a very approximate one.

But if I were to chose a method I would chose estimate by time. The reasons are, time is a universally known gauge and doesnt need to be calibrated; when new members enter your team with story points they need to be taught what your story base point is, whereas with time you dont; if you have more than 1 team in your company each team may have a different story base point and so if you move staff around teams this can be confusing for the team members and lead to inaccuracies. Another benefit of using time is that this can be used to calculate forecasted budgets much easier, whereas if you use story points you first need to translate this into its equivalent time then to work out the forecasted budgets. Of course you could argue if you are working on a set sprint length of say 2 weeks and you can complete 5 story points per person in that 2 weeks then this is the only translation into time that you need.
As it comes closer to the project development start date more finer detail of the requirements are gathered and the stories are broken down into small individual tasks.
Some teams believe they only need to refine the story points they gave at the beginning and then calculate how many stories they can fit into a sprint, based on the priority of the stories.
I agree on the overall concept of this but I believe the individual tasks should be sized themselves. The only issue here if you use story points you can a scenario where you have 0.1 story points and so this undermines the value of using story points on Tasks of the Stories.

Many teams dont bother entering their actual time spent on Tasks or Stories. Is it really required if you say you are going to deliver 15 Story points in a 2 week sprint and that is exactly what you do deliver, does it really matter if you log your actual time. Well I would argue it does.
Say for example you have 2 Stories and say you use time to size Stories, if you estimate that both Story 1 and 2 will take 1 week each to complete, but in reality Story 1 took just 2 days to complete but Story 2 took 8 days. Both Stories were still completed exactly on time that was estimated, but actually in reality the team is very bad at estimating and this should be improved.
In the next sprint the team could get it very wrong and grossly under-estimate both Stories and only deliver 1 of them.
The trade-off however is the extra administration time required to enter actual time worked.
So on balance I would suggest use time to estimate both Stories and Tasks. Start with entering Actual time until you prove the accuracy of your estimating at both the Story and Task level. Once you prove a consistently high % accuracy level across all team members you can remove the extra administration required to log actual time. Of course if new your team changes considerably you may need to restart the actual time logging for a period.

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