It's become the mantra of some in agile development community recently to *count stories* and stop counting *Story Points*.

While Story Points are Ordinal numbers and have several flaws at their core, counting Stories alone, without some supporting statistics is also flawed.

Let's start with distinguishing between *Cardinal* and *Ordinal *numbers...

When we hear about *adding* Story Points, another caution is needed ...

- An
**Ordinal**number ‒ a Story Points ‒ denote the position of an element in an ordered sequence- Ordinality involves sets and order relations on those sets.

**Cardinal**numbers ‒ natural numbers ‒ measure the*size*or*Cardinality*of sets. The possible collection of values describing an entity – the cost, the duration, the performance or efficiency measures.- There is a cardinal number for every possible cardinality.
- A cardinal number is a family consisting of all sets that can be put into one-to-one correspondence with each other.

**Why we can't do Arithmetic with Ordinal Values (Story Points) in Number Theory**

For example

Your breath smells like a funny color

orThe number 9 is Slippery

Finally, before moving to the need for Median and Mode, Stories, Story Points, and Velocity are NOT Units of Performance outside a single Scrum Team, which has calibrated Story Points to their own usage and need.

- Story Points are Ordinal numbers ‒ relative measures of effort or complexity defined by the Scrum Team members for a specific Sprint, Feature, and perhaps a Release.
- Story Points are not scope for the project, they're not calibrated to Time and Money outside an individual Scrum Team.
- Counting Story Points is like counting
*Tasks*in an Integrated Master Schedule.- We have 40 tasks to do for this delivery which is 9 weeks long (3, 3 week Sprints).
- We’ve done 20 Tasks so far
- Are we 50% complete for the planned task work?
- Not likely unless each Task is the same effort and duration and the Task variance is not significant.

**Counting Stories has the Same Problem**

The number of Stories represents Ordinal numbers as well. So those measures are *localized* ordinal values as well:

- In this release, we have 12 Stories to implement the Feature.
- We’ve completed 6 of the 12 Stories.
- Are we 50% complete with the Feature?
- Not likely, unless each Story is of equal effort and duration and each story has identical irreducible and reducible uncertainty that impacts cost and duration.

**Now the Next Problem**

When we're counting stories we need to know the *actual effort* or *duration* the stories in the past took to complete. This measure - the Cardinal Value from that measure of the Story - we can calculate the Variance and Standard Deviation of that effort and duration. With these numbers - the Cardinal measure of effort, the variances between all the Stories in the past, we can use that information for the future

Only with the Mean, Median, and Mode of a past performance time series can we make decisions or forecasts about the future performance of similar work.

Here's an example of a past performance time series and the *cone* of uncertainty in the future from that past performance. In this case the *index* of a ratio of actual to planned over a period of weeks and the possible outcomes in the future for that same index. Where 1.0 is Actual estimate = Planned Estimate