Agile Estimating + Planning - The Planning Fallacy

Episode 119 - 28 Mar 2018

Today we'll meet Daniel Kahneman. (He's a Nobel Prize winner, so he's kind of a big deal.) His work help us to understand why estimates are so often wrong. Really wrong.

I am terrible at estimating. But I take comfort from the fact that you’re terrible at estimating too.

Welcome to Development that Pays

My name is Gary Straughan

And welcome back to this “mini-series” on Agile Estimation and Planning.

If you missed the first episode

this link will take to you to in and deliver you automatically right back to this point.

It’s a while since we’ve seen the Lego team.

Let’s bring them back in,

Our hero, the developer in blue

Is working on an important feature.

Not an improvement to an existing feature. A brand new features.

A feature that - with a bit of luck - will be a game-changer for the business.

And then it happens.

A sequence of events…

that may be familiar to you.

The Boss asks the Product Owner a question:

“When will it be ready?”

The Product Owner seeks out the blue developer.

And asks him a question:

“When will it be ready?”

The Blue developer thinks about it for a moment and says...

We’ll come back to this in a moment.

This is Danny Kahneman

Nobel Laureate, no less.

Early in his career, he was part of a team working on a new textbook

  • a new university curriculum.

A year in, and the the project was going well.

Kahneman had the idea of asking the team a question.

The question was, more or less

“When will it be ready?”

He didn’t ask the question in open forum;

Each of the team wrote their answer on a piece of paper.

When Kahneman read the responses

He found they were in broad agreement

Everyone thought it would take 18 months to 2.5 years to complete the project.

Now, one on the members of the team was the Dean of the School of Education.

And it occurred to Kahneman to ask him another question.

He asked if he could think of other teams that have done what we’re trying to do?

And he said that he could

How did they get on?

Well… not all of them succeeded.

About 40% of them… gave up.

And those that succeed?

The Dean couldn’t think of ny that took less than 7 years.

Khanman realised that something funny was going on here:

The Dean had all the information he needed to make a much better estimate.

But he - like the others - had estimated between 18 months and 2.5 years.

Khanman went on - with long-time collaborator Amos Tversky - to study this phenomenon in detail.

And in 1979 they proposed the Planning Fallacy.

As Wikipedia puts it:

“a phenomenon in which predictions about how much time will be needed to complete a future task display an optimism bias and underestimate the time needed.”

So when the Boss asks the Product Owner “When will it be ready?”

And the Product Owner asks the Developer “When will it be ready?”

The answer that the developer gives is high likely to be wrong.

It’s likely to be far too optimistic.

Even if the developer knows that similar tasks performed by others have taken longer.

Indeed… even if the developer knows that similar tasks performed by HIMSELF have taken longer.

(Or herself,. I do try to me gender- neutral around here. But this one looks like a guy to me.)

So this sequence of questions is, at the very least, not helpful

Just pause for a moment and think about how you feel about that.

Perhaps you think that this question is more than reasonable. That you need some measure of predictability to do your job.

Or perhaps your in this position - the Product Owner.

Perhaps you’re feeling just a little bit insulted,

because you’d never ask a developer for an estimate - at least, not in this way.

Or perhaps you’re thinking something else.

If so, I’d love to know what it is. Let me know in the comments below.

// Add in the end

Is there a way to give each of these people what they need?

I’m not sure… but we’ll take a step in that direction in the next episode.

If you enjoyed this epsiode, please give it thumbs up.

Share it with your network.

And hit the logo right here

For a new episode every Wednesday.

Cheers for now.