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- Generally speaking,
people aren't very good at making absolute estimations.
It's really hard to estimate accurately
exactly how long something will take to get done.
In traditional project management,
we knew this,
so we cushioned our estimates
by hours, days, or weeks
in the hope that we'd be somewhat close.
Agile addresses this fundamental human behavior
by acknowledging that,
while people stink at absolute estimation,
we're really good at comparing things to each other.
This is known as relative estimation.
Agile teams rely on this type of relative sizing
to be faster and more accurate with their estimates.
As an example,
a soccer ball is roughly three times bigger
than a cricket ball.
Story points are the most commonly used measurement.
They're based on the Fibonacci sequence of numbers
or some variation of it.
This sequence is a naturally occurring numerical pattern
that accurately reflects how things grow.
It's really a simple math process.
The next number is the addition of the two previous numbers.
So the sequence is 1, 2, 3,
5, 8, 13, and so on.
Using this sequence and knowing the pattern,
we can start comparing things.
If a golf ball is one,
then I'd say a cricket ball is a two.
What about a soccer ball?
Well, since it's about three times bigger than a baseball,
I'd say, it's an eight.
Relative sizing is the foundation
of all estimation techniques used in agile.
Other techniques can be used just as successfully.
So let's look at a couple.
First, let's talk about affinity estimation.
This technique involves grouping your stories
into similar categories or affinities.
There are many ways to do this,
but the technique is very simple.
At one end of the whiteboard or wall,
you'll place all your stories with a size of one.
Next to them, the twos,
then the threes and so forth.
As you continue to estimate the stories,
they'll be placed on the wall in the right size affinity.
As you add stories,
you're comparing them to the ones already there.
Does it fit?
Does it seem bigger or smaller
than the story's already there?
If something doesn't seem to fit,
the team will hold a discussion to make changes.
In this way, we get a reality check
to make sure our estimates are consistent.
Another technique that can be used
is known as Wideband Delphi.
This is a group-based estimation technique
where a panel of experts, your team,
anonymously submit their estimates.
The reason this is so valuable
is that it avoids human biases.
The common biases we're trying to avoid
are the bandwagon effect,
where people tend to go along
with whichever opinion is gaining the most ground.
There's also HiPPO decision-making.
HiPPO stands for highest paid person's opinion.
And as you can guess,
people tend to defer to them as being experts
as well as superiors.
And group think,
where people make decisions to keep harmony
instead of voicing their true opinions.
These behaviors will skew the accuracy of the estimates
and impede the progress of the team.
Few teams actually use Wideband Delphi for their estimates.
Most teams use one of its related techniques.
That technique is planning poker.
It's the most commonly used agile estimation technique.
All of these techniques are designed
to help teams produce fast, easy,
accurate estimates for their work.
Because they're simple to use and easy to adopt,
you can use these techniques
to help your team improve their accuracy too.
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