A talk by John Coleman on the InfoQ article on sizing and forecasting in Scrum at https://www.infoq.com/articles/sizing-forecasting-scrum/

1. Estimation is dead
- long live sizing
John Coleman
@JohnColemanIRL
https://linktr.ee/johncolemanxagility
https://www.infoq.com/articles/sizing-
forecasting-scrum/

2. How many minutes did
it take me to paint this
trellis?
• Front and back
• One generous coat of paint
• Get every little groove and corner painted without
having paint all over the floor
• Must pass independent inspection

3. Estimate is no
longer in the
Scrum guide
Product Backlog
The Product Backlog is an emergent, ordered list of what is needed to
improve the product. It is the single source of work undertaken by the
Scrum Team.
Product Backlog items that can be Done by the Scrum Team within
one Sprint are deemed ready for selection in a Sprint Planning event.
They usually acquire this degree of transparency after refining
activities.
Product Backlog refinement is the act of breaking down and further
defining Product Backlog items into smaller more precise items. This
is an ongoing activity to add details, such as a description, order, and
size. Attributes often vary with the domain of work.
The Developers who will be doing the work are responsible for the
sizing. The Product Owner may influence the Developers by helping
them understand and select trade-offs.

4. Forecast in the Scrum guide
The Sprint
Various practices exist to forecast progress, like burn-downs, burn-ups, or cumulative flows. While proven useful, these do not
replace the importance of empiricism. In complex environments, what will happen is unknown. Only what has already happened
may be used for forward-looking decision making.
Sprint Planning
Selecting how much can be completed within a Sprint may be challenging. However, the more the Developers know about their past
performance, their upcoming capacity, and their Definition of Done, the more confident they will be in their Sprint forecasts.

5. So is
estimation
dead?
First, let’s look at sizing

6. Sizing caveats
People who do the work do the sizing, no one else!
Complex work is uncomparable - when dealing with complexity, know that these
techniques are almost always inaccurate
If we don’t ”clean up up the kitchen” as a habit, the accumulation of mess will
lead work will take longer than before
The most popular sizing techniques are either based on data or educated
guesses

7. Sizing options
Relative estimation
Flow metrics or counting valuable items
Rightsizing
#Noestimates

8. Flow metrics -
Kanban Guide for
Scrum Teams
Throughput: The number of product backlog items finished
per unit of time
Cycle Time: End-date minus Start-date +1
Work Item Age: The elapsed calendar time between when
a work item started and the current time; this applies only
to items still in progress
Work in Progress (WIP): The number of work items started
but not finished

9. “Kanban
board”

10. “Work In Progress”

11. “Cycle Time”

12. Work Item Age

13. Throughput

14. Flow metrics

15. Relative
estimation
1 of 2
Time reference - Comparing current work
items to the time it took to complete historical
reference items
Assigning numeric values - Examples include
using story points based on the Fibonacci
sequence and often carried out collaboratively
with playing cards (planning poker)
T-shirt sizing - Assigning s, s/m, m, m/l, xl, xxl,
xxxl, xxxxl to Product Backlog Items instead of
numeric value
Wall estimation - Assigning numeric values by
collaboratively placing and moving cards on a
wall, also referred to as magic estimation or
silent estimation

16. Relative
estimation
2 of 2
It comes in different flavors
If you estimate, the best thing that can happen is the
estimates are correct
Estimates are prone to the "flaw of averages" (Sam
Savage). Is 50:50 an excellent way to set expectations?
The average of independent blind assessments can be
near enough to the truth (credit to Dave Snowden) -
how often estimates blind in Scrum Teams though
If you don't estimate at all, you don't waste time;
hopefully, you will discover/deliver outcomes sooner

17. Rightsizing
How much time could you save caring more about whether
the team can complete an item within the Sprint and less
about making that item infinitely smaller?
Think of the reduced cognitive load on the Product Owner
resulting from fewer PBIs
Counting the number of (valuable right-sized) PBIs delivered
to Done per Sprint is valuable for Sprint Planning and
forecasting goals
If throughput is sporadic or irregular, we have more significant
problems than forecasting; we have a "plumbing problem"
Using average throughput also pursues the "flaw of averages;"
Monte Carlo probabilistic forecasting is preferable

18. One interpretation of
#NoEstimates
STRIVE FOR AN EVEN
DISTRIBUTION OF
"BALLPARK" ITEM SIZES
THROUGHOUT A
BACKLOG
COUNT RUNNING TESTED
STORIES OR RUNNING
TESTED FEATURES TO
DEMONSTRATE
PROGRESS IN OUTPUT
TERMS
FOCUS ON SIMPLIFYING
THE WHAT FOR THE WHY -
A FOCUS ON DESIRED
OUTCOMES
RIGHT-SIZING - IDENTIFY
SMALL ENOUGH ITEMS
FOR INTAKE
SLICING INTO 24-HOUR
TIMEBOXING OF ITEMS
ENCOURAGES THE
CREATION OF
EXPERIMENTS THAT
VALIDATE
ASSUMPTIONS/HYPOTHE
SES TOWARDS A GOAL,
DISCOVER TO DELIVER
USE ROLLING-WAVE
FORECASTS TO
COMMUNICATE
UNCERTAINTY

19. One
interpretation
of
#NoEstimates
• Counting the number of (valuable right-
sized) PBIs delivered to Done per Sprint is
valuable for Sprint Planning and
forecasting goals
• "Rolling Wave Forecast” based on
throughput with variance limits is
preferable

20. Time reference
Potential downsides
Requires suitable reference items from the
past
Prone to abuse be people with a focus on
people utilization
Unsuitable for probabilistic forecasting
Potential upsides
Speaks in the customers language
Easy to pick reference items from the past
Waiting time is included in our memory of
how long it takes
Simple to do

21. Story points
Potential upsides
Useful to avoid bringing “elephants” into WIP
Could be used to limit work in progress
Easy to pick reference items from the past
Simple to do
Developers like the conversation it triggers
Often paired with t-shirt sizing or wall
estimation
Could be combined with probabilistic
forecasting, but should it?
Potential downsides
Creator regrets story points
Only for the team
Story point inflation
BS story points
Often paired with planning poker (time
consuming)

22. T-shirt sizes
Potential upsides
Useful to avoid bringing “elephants” into
Work In Progress
Could be used to limit work in progress
Easy to pick reference items from the past
Developers like the conversation it triggers
Simple to do
Requires very little detail
Potential downsides
Converted to numbers quite often, numbers
that get used to forecast when work might
be done

23. Wall / table estimation
Potential upsides
Useful to avoid bringing “elephants” into Work In
Progress
Could be used to limit work in progress
Easy to pick reference items from the past
Developers like the conversation it triggers
Simple and quick to do; requires very little detail
Guesstimate for potential value sized as well as
effort typically, priming ordering for value divided
by size
Potential downsides
Converted to numbers quite often, numbers
that get used to forecast when work might
be done
Often one and done – should be revisited
regularly

24. Guesstimating / counting the number/
range of items to deliver a goal
Potential upsides
Suitable for recurring probabilistic
forecasting or rolling-wave forecasting,
giving dates and uncertainty
Developers can “ballpark” the range
Useful for sizing a chunk of Product
Backlog, e.g, “elephant” sized items in the
Product Backlog
Can be used across teams
Potential downsides
People prefer relative sizing, and almost
“cannot let go”
Misunderstood that all items need to be of
equal size
For non-software different product backlog
item render it like comparing apples with
oranges
Prone to the use of averages

25. Rightsizing
Potential upsides
Simple
Less “analysis paralysis”
Supports recurring probabilistic forecasting
Potential downsides
Items right-sized just in time or in product
backlog refinement
Misunderstood that all right sized items
must be of equal size
Disconnect in Kanban community about
use of item split rate to support
probabilistic forecasting
If most days a team has no throughput,
probabilistic forecasting will have low
quality

26. #NoEstimates
Potential upsides
Split items as necessary, potentially into
discovery items
Small batch is the goal
Forecasting using data – “running tested
stories”
Accepts uncertainty and imperfect information
Useful for recurring forecasts
Low time investment
Seeks a mixture of item sizes
Potential downsides
In the wrong hands, splitting items into
nonvaluable items
People prefer to be wrong than uncertain

27. So is
estimation
dead?
Now, let’s look at the disparity between
sizing and how long work takes

28. “John, that’s
about ten
minutes of work,
but things are so
crap around
here, make that
three days”
Estimated effort has little to do with how
long something takes

29. Variable quality with sizing an item
Factors for how long things take
The batch size – the level of effort actually needed
Waiting
time
…
Sizing for the level of effort considers
Complexity of the work
Riskiness of the work
Whether we did something similar before
Perception of skill levels required to complete the
work and availability of those skills
Availability of tools and skills using those tools
If you’re good, dependencies

30. 100% Resource utilization = 0% flow
(Henrik Kniberg)
Image courtesy of LeSS.works

31. Utilization of
people
Credit - the LeSS Company - LeSS.works

32. Utilization of
people
Credit - the LeSS Company - LeSS.works

33. Waiting time
Reduced by
Working on smaller batches
Working together
Leaving slack so people can help each other
A better understanding of how the work works
Active management of work in progress
Flow review & improvement rigor
Starting work mostly when we have
• capacity to start
• alignment with our dependency partners
• alignment upstream and downstream
Increased by
High utilization of people
Pushing work into the system before capacity
allows for anyone who does work on the item,
including final review
Lower quality of in progress queue management,
e.g., re-prioritizing in-progress items based on
potential value
Lower quality of dependency management /
elimination
Contradictory management of the level of
constrained-resource or shared-resource queues

35. If your forecasts are routinely
correct, you're a freak of nature
Forecasting is rarely perfect due to the following:
•Waiting time due to dependencies is a huge factor in how long work takes and is affected by many
unpredictable events.
•Even in straightforward work environments, people overestimate how efficiently their day will go.
•Often, people doing complex work in the pursuit of speed leave work behind them that is untidy and
potentially embarrassing (accidental complication).
•Complex work involves many unknown variables.
•Lack of focus
•Changing priorities

36. Monte Carlo simulations
model a future based on
data and assumptions

37. Monte Carlo simulations
model a future based on
data and assumptions
Forecasting, at its essence, is
about risk management
It answers the question - How
much risk is contained in our
current plans?
Lower quality forecasts also
mean inadequate risk
management

38. Estimation
qService Level Expectation based on an educated guess, e.g., 85% of right sized items are done
in 18 days or less
qIndividual item sizing – useful if you only need to focus on one next unstarted item
qGuesstimate Probabilistic item forecast - guesstimating a range of a number of valuable items
to deliver a goal, with 90% confidence min/max
qProbabilistic guesstimate story point forecast - guesstimating a range of a number of story
points to deliver a goal, with 90% confidence min/max
qStory point range - guesstimating a range of a number of story points to deliver a goal and using
probabilistic forecasting with 90% confidence min/max
Options for managing expectations

39. qService Level Expectation based on cycle time data, e.g., 85% of right sized items are done in 18 days or less
qIndividual item age – useful if you only need to focus on one next started item but unfinished item
qData Probabilistic item forecast - 90% guesstimating a range of a number of valuable items to deliver a goal, based on throughput data of valuable
items
qRolling wave forecast - Throughput data range - 90% guesstimating a range of a number of items to deliver a goal and using throughput data
qThroughput data average - Best guess of number of valuable items divided by average throughput data (number of items done) per
day/week/sprint/month…
qProbabilistic story point forecast - 90% guesstimating a range of a range story points to deliver a goal and using probabilistic forecasting based on
story points data
qStory point data average - Best guess of number of story points divided by average number of points really done per day/week/sprint/month…
qCounting subtasks - Best guess of number of non-valuable items divided by average throughput (number of non-valuable items done) per
day/week/sprint/month…
Options for managing expectations
Forecasting

40. Estimation
qService Level Expectation based on an educated guess, e.g., 85% of right sized
items are done in 18 days or less
qIndividual item sizing – useful if you only need to focus on one next unstarted item
qGuesstimate Probabilistic item forecast - 90% guesstimating a range of a number
of valuable items to deliver a goal, based on guesstimate min/max range of valuable
items
qProbabilistic guesstimate story point forecast - 90% guesstimating a range of a
number of story points to deliver a goal, based on guesstimate min/max range
qStory point range - 90% guesstimating a range of a number of story points to deliver a
goal and using probabilistic forecasting based on guesstimate min/max range
Forecasting
qService Level Expectation based on cycle time data, e.g., 85% of right sized items
are done in 18 days or less
qIndividual item age – useful if you only need to focus on one next started item but
unfinished item
qData Probabilistic item forecast - 90% guesstimating a range of a number of
valuable items to deliver a goal, based on throughput data of valuable items
qRolling wave forecast - Throughput data range - 90% guesstimating a range of a
number of items to deliver a goal and using throughput data
qThroughput data average - Best guess of number of valuable items divided by
average throughput data (number of items done) per day/week/sprint/month…
qProbabilistic story point forecast - 90% guesstimating a range of a range story
points to deliver a goal and using probabilistic forecasting based on story points data
qStory point data average - Best guess of number of story points divided by average
number of points really done per day/week/sprint/month…
qCounting subtasks - Best guess of number of non-valuable items divided by average
throughput (number of non-valuable items done) per day/week/sprint/month…
Options for managing expectations

41. Better options
Manage expectations about uncertainty not
dates
qWe're using an empirical approach
operating one Sprint at a time
qThe Sprint Goal is not even a guarantee
qThe real answer is we don't know, but let's
start and learn quickly"
qYou might not even use Now?, Next ??,
Later ???
Being agile - don't manage expectations at all,
let people go see
qDiscover and deliver capabilities
qReview outcomes with the customers and
end-users
qLearn what can be learned
qAct on what we have discovered

42. Sizing is
devalued by
•Not having caveats associated with the start date,
e.g., nine weeks from the date we start
•Not recognizing the amount of work in progress and
the progress (or not) of that work
•The severity of impediments
•Not ordering items higher up the Product Backlog
according to delivery risk
•A sub-optimal approach to handling dependencies
•Confusing outputs with outcomes; a customer/end-
user outcome is a change in customer/end-user
behavior
•Not engaging in discovery activities when the risk of
not harvesting potential value is high, compounded by
assuming that every item moves from discovery to
delivery
•Delusions of accuracy and pursuing more accuracy

43. Key take aways Avoid story points, counting non-valuable product backlog
items, counting unDone work as Done, use of averages
Avoid
Consider historical reference items but beware
of accidental complication
Consider
Try probabilistic forecasting based on counting valuable
product backlog items to Done
Try
Try #NoEstimates and “rolling wave forecasts” of valuable
product backlog items to Done
Try
For complex work, promote managing expectations about
uncertainty over managing expectations about dates
Promote

44. Techniques to
challenge
forecasts
Scenario planning
Threatcasting
Future Backwards
Ritual Dissent
Cynefin
Reality Tree

45. Thank you
John Coleman
@JohnColemanIRL
https://linktr.ee/johncolemanxagility
https://www.infoq.com/articles/sizing-forecasting-
scrum/

46. Appendix

47. About me
agility chef, executive agility
guide, product manager
#2 Agile Thinkers 360, Top
50 Agile Leaders
Leadershum
Flight Levels Coach,
ProKanban Professional
Kanban Trainer, Scrum.org
Professional Scrum Trainer,
LeSS Friendly Scrum
Trainer
author of Kanplexity™,
underpinned by Cynefin®
creator of Xagility™ co-author of Kanban Guide
Host of Xagility™ & Agility
Island podcasts
Organizer for Meetup LeSS
Baku Meetup group which
was active during covid - an
official scrum.org
community and an official
LeSS meetup

48. Ideal time
Potential upsides
Time is what the customer wants
Simple to do
Potential downsides
When was you last ideal day?
Does not include waiting time, the 90+%
contributor of how long work takes
Doesn’t help infer when the work might be
done
Supports a people utilization mindset

49. Cost estimation
Potential upsides
Time is what the customer wants
Simple to do
Estimating the number of sprints could be
useful for commercial bids for example
Potential downsides
Less useful for actionable Product Backlog
Items that would go into a sprint

50. Three point (min, mid, max)
Potential upsides
Reveals some of the uncertainty
Room for optimists and pessimists
Does not use averages
Can be used for number of items, number of
story points, ideal time, reference items
Waiting time is included in our memory of how
long it takes
Simple to do
Can be converted to story points
Potential downsides
Average performance often used against
mix/max sizes for forecasting afterwards
Only for the team
Prone to inflation
Can be converted to story pointsJ

51. Get stronger flow...
without adding more people
Better to have slack than overwhelm, so
people have time to help each other
Split items into smaller but still valuable
items when needed
Show empathy within the workflow, but
also upstream and downstream
Look after aging
• unblock, focus, finish / cancel
• do ensemble work
Don’t forget to feed the system
Lower aging =>
Lower cycle times =>
after a time-lag ...
More stable throughput… then
higher throughput
Prioritize within throughput, adjust
for noise

52. Other sizing
sub-optimal
trends
•Size per skill - typically caused by focus on resource
efficiency over flow efficiency
•Size inflation. In extreme cases, I refer to this it’s as
bingo
•Not taking quality seriously- typically caused by
pressure for more "velocity"
•Not taking the customer seriously
•Size normalization across teams
•Counting complete but fake product backlog items,
items that don't deliver value, as throughput
•Not focusing, not finishing
•Delusions of predictability for work that is
uncomparable with work from the past
•Lack of discovery to find the items we maybe should
not build; if we run low-cost experiments, we might fall
upon better ideas

53. Community
opinions on
Monte Carlo
simulations
Communities are not aligned on this approach.
One project is only executed once
While probabilities may help inform decisions,
the problem is that they don't make the
decision any easier
Estimation is often used as a proxy for a
decision (should we do this project or not?)
The reasons for using estimates differ from
probabilistic forecasting.
I have seen many probabilistic forecasts based
on guesstimates and a lack of history, yet they
were not far off in the end

54. Often there is
another question
behind the
question “when
will it be done”,
such as:
•How can I transfer worry to someone else?
•What progress is being made?
•What risks remain?
•When will we get some return on this investment?
•What trade-offs can we tolerate regarding which work
can discover/deliver the potential value, e.g., the 80:20
rule?
•What trade-offs can we tolerate in terms of reducing
some or all of effectiveness, efficiency, and
predictability, e.g., running some experiments?
•What progress trade-offs can we tolerate in terms of
required "dead work" to avoid execution bias, such as
laboratory setup?
•How much investment will go into acquiring skills,
e.g., education or apprenticeship?

55. A meta-question
of "what does
winning the game
mean?" is well
worth considering.
Is the team being given a game it can win?
And if the team can win, what are the odds?
Probabilistic forecasts can help, e.g., Monte-
Carlo simulations
Despite the hazards, people fear that
stakeholders will make up arbitrarily fixed
undoable dates in a vacuum
Sometimes teams want to attain a ballpark
date range to get ahead of stakeholder
expectations
Interestingly, most of us can accept a weather
forecast that gets updated regularly based on
the latest information