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Product owner reviews product backlog items with the team for clarification and revision. The team estimates the effort of each item.
Key Ideas
Planning poker: a “game” where each team member uses a card to show their estimate of the work involved in an item
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As we've discussed before,
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the key contribution of the product owner
is to maintain the product backlog.
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The product backlog is
a priority ordered list of items
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that the team will eventually
pull into a sprint to complete.
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Product backlog items may include defects
and technical items or technical debt.
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As we learned before,
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items that describe value to the user
are described in user's stories.
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User stories are a special type of
product backlog item that describes who
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will use the feature and why.
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We'll learn more about how to construct
user stories later in the course.
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For now, we'll look at the Scrum event
where these stories are discussed, or
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the backlog refinement session.
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Backlog refinement is also sometimes
called backlog grooming, or
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more playfully, story time.
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However your team chooses to name
the event, it is an opportunity
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to review product backlog items,
get input from team members,
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add clarity to the items, and
estimate the effort involved.
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The product owner drives
the conversation in backlog refinement.
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The goal is to refine items in the backlog
so that they are well understood, and
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small enough to be
incorporated into a sprint.
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Generally, the product owner will begin
with the items in the backlog that
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are coming up, but may also incorporate
new items or ones that he or
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she anticipates will require a few passes
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before they are ready to
be taken into a sprint.
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During backlog refinement, the product
owner presents a product backlog item or
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user story.
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The product owner opens
the floor to the team and
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answers clarifying questions about what
the story means or what it entails.
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If the story is too big,
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the team discusses how it can
be broken into smaller pieces.
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The team checks their shared understanding
by drafting conditions of acceptance, or
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acceptance criteria.
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These describe
the characteristics of a solution
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without saying how
the problem will be solved.
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For example,
a condition of acceptance might be
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that the user sees relevant articles
when they type a support question.
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This is something that can be tested
later, without having to work out all
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the details of where the relevant articles
are presented or how they will appear.
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After a few items have been discussed, the
team estimates the effort of each item.
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There are many ways to estimate effort.
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The most popular method is
probably Planning poker.
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In Planning poker, each team member
gets a set of cards with story points or
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effort points on it.
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Each team member chooses one card and
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displays it to the rest of the group,
showing their estimate of the amount of
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work involved in a particular user
story or a product backlog item.
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Story points are relative
estimates of the amount of
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effort it will take to complete an item.
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In Scrum, we use the story points
in place of time based estimates,
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such as hours, because we recognize that
those estimates are likely to be wrong.
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It's much easier to compare two items and
say that one requires a little more effort
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than the other, or that one requires
twice the effort of the other.
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Generally, story points are assigned using
a series where the steps increase in size.
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This is because as we get
into higher estimates,
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we recognize that we really don't know
how much effort something will take.
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And in fact,
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the item may need to be broken up into
smaller parts in order to be estimated.
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An example number series used for
story points is the Fibonacci sequence.
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The Fibonacci sequence is a series
of numbers where each number
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is the sum of the previous
pair of numbers.
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Don't worry too much about
the meaning of the Fibonacci numbers.
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There's a mathematical allure
to the Fibonacci sequence,
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which you may be interested
in reading about.
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But in this case,
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we really just need a number sequence
where each step is progressively greater.
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That way, we can easily compare
the effort of two product backlog items.
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In fact, another sequence of numbers
is also commonly used in Planning poker
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based on powers of two, where each
number is the double of the previous.
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Again, the most importing thing here
is to be able to compare the effort of
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one item to another.
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For example,
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this story is twice the effort of another
story because when team members display
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their effort estimates in Planning poker,
the team tries to reach consensus.
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Often, the facilitator will ask
team members with the highest and
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lowest estimates to
explain their reasoning.
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For example, the Scrum master
might facilitate by asking,
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your estimate is lower than the others.
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Is there anything about your
thinking that you can share?
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This is another opportunity to
come to a shared understanding
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on the product backlog item and
the work it entails.
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