**Counting, positioning, or measuring**: what's in a number?

Remember pre-school or kindergarten: we all "learned our numbers".

Ah! but did we?

**Want to count something?**Just use the integers, starting at 0 and going in familiar step: 1, 2, 3 ....

The count takes on the dimension of what you are counting: dollars, inches, meters, liters, etc

*You can do arithmetic on count*, but because of the dimensioning, the results may or may not be viable: square inches are ok, but square dollars are not.

**Want to rank or position something?**Again, we fall back to the integers -- 1st or 2nd position is good; position 1.2 in a queue has no meaning or implementation. And, there is no dimension per se in a position. Some arithmetic still applies, but it's tricky. Addition is not commutative: you can add 1 to first position to get second position, but you can't add first position to a 1. Stuff like that.

**Want to measure something?**You can use any rational number (a number that can be fashioned by the ratio of two numbers). Really, anything on a measurement scale is rational and can be a measurement. And, you can do arithmetic between rational and irrational numbers (like "pi")

For a number to be useful in measuring, every number in between has to be meaningful. That's why you don't do measurements with ranks and positions: the in-between numbers are not meaningful.

**Calibration:**And, to be meaningful, the

**scale has to be calibrated**. A ruler with irregular spacings or a warped or bent rule, or guesses without reference to benchmarks or other reference classes are uncalibrated. And, thus, every number in between is not meaningful.

**Project management**

And so, where does the rubber meet the road in project management?

- Probability x impact risk tables or matrices
- Planning poker

Answer:

- If for real measurements, you need to
**normalize the reference class or benchmark**to the project. - But, if for ranking or positioning, nothing more is needed

**1-2-4-8**

Just about every planning poker game or risk matrix uses some simple scale, like the binary scale, to weight the choices or impacts. Fair enough

But, a "4" in one project may have really no relationship to the value of a "4" in another project. So, are these numbers just ranks, or positions, or are they numbers for measurement?

If just for ranking, then nothing more is needed: 4 ranks over 2 by 2:1. Done

If for measurement, then here's what you do:

- Find the simplest real thing you've done before that is similar and call it the baseline cost; divide its cost by its cost. You'll get 1, of course
- For everything more complicated, divide by the cost of the baseline. Something twice as hard should divide out as a 2; four times harder divides out as 4.

We're done here!

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