Agile estimationPrinciples

Cone of UncertaintyV

aria

bilit

y of

Est

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es

Time to CompletionDONE

Where is Irene going?

Where is Irene going?

Where is Irene going?

Precision And Accuracy• Your mind is not a precise

time-estimating tool• Your mind can be an accurate

time-estimating tool• Trade precision for accuracy

to succeed

Point of Diminishing Returns

Time

Acc

urac

y of

Est

imat

es

Stop here

Relative estimation

It’s easier to estimate unknown things by comparing them

relatively to things you know

Discussion is the Key• Having group discussions flushes out• Unknown facts• Different points of view• Common understandings

• All opinions are valuable• What happens if only the expert estimates?

An Abstraction: T-Shirt Sizes• S, M, L, XL• Maybe XS and XXL? Be careful of the trap of perceived

precision…• Note: there are no sizes in between major divisions

10 minWall Estimation Technique

• Create a board with 4 T-shirt sizes as columns (S, M, L, XL)• Write the following objects on individual sticky notes,

and put them in appropriate columns based on size• Asia• A 2007 Toyota Prius• The White House• Arkansas• 1977 Cadillac Eldorado• New Mexico

• The Pentagon• All of the Great Lakes• Australia• A one-car garage• Indian Ocean• A Junior High baseball field

An Abstraction: Story Points• A Story Point is a very commonly used abstraction for

agile estimation• On what is a “Story Point” based?• Complexity• Risk• Unknowns• Effort• Cost• All of the above!

Story Points• Using the Fibonacci sequence is common • (0, 1, 2, 3, 5, 8, 13, 21…)• This represents the Cone of Uncertainty• The numbers represent classes of size, no units in between

Comparing AbstractionsAbstraction Classifications UnitT-Shirts • S, M, L, XL Size

Story Points • Typically numeric, in a FibonacciSequence

• i.e., 0, 1, 2, 3, 5, 8, 13, 21

“Story Point” – AKA, some combination of • Complexity• Risk• Unknowns• Effort• Cost

Abstraction advantages• Abstractions prevent unintentional time commitments• Keeps us in a relative estimation state-of-mind• Provides protection against Parkinson’s Law• Allows us to be empirical using new information as it is

available• Saves us from endless re-estimating

Solving for Time later…• Most questions around estimation are questions about

time to complete• We can answer the real question without having to

estimate directly in time units!• Let’s solve for time last

Story Points != Unit of Time• Distribution of time taken to complete a 5 point story

Time

Story Points != Unit of Time

Time

5 8

Story Point Anti-Patterns• Solving for time up front• It’s unsafe to normalize story points (bad SAFe joke)• Story points are intentionally unit-less and relative to each

other• Taking a number in-between• Putting new numbers in between the sequence adds false

precision.

Planning Poker• Another estimation technique• Based on difficulty for the team, not for individuals• Good for diving deeper into PBIs

• The development team doing the work estimates• PO should be available for questions

Technique: Planning Poker• Discuss the story briefly• Each person on the Dev Team selects a

card • Team reveals their selections all at

once• Outliers explain their selection to the

group• Repeat steps 2-4 until (near) consensus• Take the closest number, not the

average

3

2

3 85

Get Ready to go to the Beach

Billy

Johnny

Suzie Carol

Dave

5

2

5 13

8

Get Ready to go to the Beach

Billy

Johnny

Suzie Carol

Dave

8

21

8 88

Get Ready to go to the Beach

Billy

Johnny

Suzie Carol

Dave

Anti-Patterns• Don’t do these:• Estimation differs based on who might

work on it• Rushing to lay down cards before

everyone is ready• One person estimates out loud,

everyone lazily agrees • Little conversation occurs• Estimation is only done with the team

lead and product owner

Anchoring• The act of influencing opinions before a decision is

made• TIP: You can use this to your advantage!• Salary Negotiations:

“Substantial psychological research suggests that, more often than not, negotiators who make first offers come out ahead” - Adam D. Galinsky (Harvard Business School)

Anchored estimates

Avoided discussions

Lazy estimates

5 minMake Your Deck Now

• Create a deck with the following cards:• 0, 1, 2, 3, 5, 8, 13, 20, 40, 100• Do not include: ?, ½, ∞

10 minEstimate this work

Estimate the following using the planning poker technique – use: 0, 1, 2, 3, 5, 8, 13, 20, 40, 100• Plant a tree• Paint the house• Clean the garage• Get ready to go to work• Replace the engine in your car