Wednesday, August 12, 2009

How to make me stupid

Technical communication is essentially story telling on one hand and sense making on the other. I've noticed (suffered at the hands of) several patterns involving numbers that obscure both.

Consider the following question, "How much does widget A weigh?"

Bad answer: "You have to understand that it will be different in different situations. If it is the blue techno-widget, it will be 30 pounds, but if it is the red techno-widget, it can be as low as 20 pounds depending on if it is a model D, which is 20 pounds or a model C which weighs 25 pounds because it has the heavy duty battery."


Better answer: "Twenty to thirty pounds depending on the model and battery type."

Common mistakes when talking about numbers

Here are common mistakes I see when people talk technical with numbers:
  • Combining numbers with conditional statements. That's the mistake in the previous example. I'm having to hold too many variables in my head before I can get closure on a declarative sentence. Lead off with a simple declaration followed by exceptions. Another acceptable answer would be "About 25 pounds." That relates a bit to the next common mistake.
  • Not rounding to a reasonable level. I sit in a lot of budget discussions where we are essentially discussing estimates and guesses and I am forced to comprehend and store numbers like 23,462 when 23,000 or even 20,000 is sufficient. Many people do not understand the rule of significant figures, that is, an answer cannot have more significant figures than are warranted by the input accuracy. For example, 10 volts divided by 30 ohms does not result in a current of .333333333333 amps. It results in .3 amps.
  • Giving algebra problems instead of answers. "Q: How much does widget A weigh? A: Ten pounds more than widget B." Great, widget A weighs x + 10, solve for x.
There is a scene in Othello where the generals argue about how many ships are in the approaching armada. The bottom line, stated more eloquently by Shakespeare is "It's a shit-load of ships." In other words, providing the exact number is less important than contextualizing the impact.


Margaret said...

I suspect that all those who grew up using digital calculators since middle school have never totally grasped the concept of significant digits. The calculator displays as many digits as there are in the LED display. Those of us who were "allowed" to use slide rules in math and physics classes also learned to pay attention to where the decimal point should be in those significant digits. I had a physics professor who gave multiple choice answers on his tests: All the answers had the same significant figures, but had the decimal point in different places.

Michael Hughes said...

I was in the last class to go through my electronics technology school with school-issued slide rules. A friend bought a digital calculator that had the four functions and a key for pi; he paid $100 for it.

BTW, I still have a beautiful bamboo Picket slide rule.