Kind of like a misnomer, but with numbers.
There are a bunch of numbers that people base decisions on (primarily purchasing decisions) that are misleading. Marketing people love these numbers, and engineers hate them, because they fool people into spending more money than they ought to. I call these numbers misleading numbers, or misnumbers.
My favourite misnumber is that of audio power ratings. You will see a hifi or amplifier rated at 80 watts per channel, another at 100W per channel, and yet a third for 120W per channel. There is usually at least a few thousand rand difference between them. Which should you buy, if you can afford all of them? The sales and marketing guy will tell you the 120W, but the engineer knows better. Much better. Without going into any technical detail, the difference in sound volume between them (assuming the same efficiency speakers) is almost imperceptible! The reason for this is that it takes double the power to get the sound to be "one notch" louder, and ten times the power to make it twice as loud. And what about those tiny computer speakers rated at 1000W? Complete marketing bull manure! The engineer looks for RMS rating, and knows that speaker efficiency is more important than amplifier power output rating. The engineer is a good friend to have, when shopping for tech!
What about car performance rating? Almost every car enthusiast I know bases their entire opinion of a car based purely on one number: how many kilowatts of power the engine puts out. In practise, I know that this number is highly overrated, and almost completely irrelevant on it's own. As an example, a Lotus Elise/Exige uses a Toyota RunX RSi engine, but significantly outperforms it. The reason is mainly because of it's lighter weight, but also because of it's better aerodynamics and suspension. My 17 year old Nissan 200SX with "only" 127kW can keep up with, if not outperform many of the "hot hatches" with significantly more power on a track or a drag strip because of a combination of several factors including weight, aerodynamics, engine power delivery, power distribution to the wheels, suspension, etc.
Another favourite car performance misnumber is top speed - practically, it is insignificant once it gets over 200km/h as even on many race tracks it's difficult to hit the top speed. The 0 to 100km/h time (or quarter mile time) is also a misnumber in that removes handling from the equation (a modified Uno beating a Ferrarri on a drag strip is not uncommon), but of all the automotive misnumbers, this is the least evil of them all. What does the engineer recommend for measuring car performance? A combination of 0 to 100km/h time and a lap time around a standard short track (like the Top Gear Test Track).
What is more important though, is that the performance differential out in the real world on a real road is almost negligible, because of speed limits, traffic, driver ability, driver sensibility, etc. If a modified sports car capable of producing 200kW opened full throttle in front of a similar unmodified 130kW car which responded in kind, the car in front would pull away at a rate significantly slower than what you would expect. Infact, for all practical purposes, up to the speed limit, any car with sufficient performance (e.g. a hot hatch or better) would be as fast as any other car on the road (including super cars). My advice is to forget trying to be faster than someone else - you are wasting your money. Instead focus on getting the most enjoyment out of your purchase. If the performance of the car you like puts a smile on your face when you test drive it, then that is all you need to know - forget the misnumbers!
I could go on and on about other misnumbers. I could talk about resolution, contrast ratio and response time of LCD TV's, gigabyte rating of MP3 players, or one of my other favourites - megahertz rating of computer processor chips. However, I want to touch on the greatest misnumber of them all - price, or more specifically, money!
Try this quick thought experiment: imagine a time when you had no idea how much houses cost, but you know you need to buy one. If you were asked how much you would pay for a 3 bedroom house in The Reeds in Centurion, what would you answer? R10,000? R100,000? R10? What if it was an auction with no reserve and no starting bid? What would your maximum bid be? No idea? So you do some research: look at the local classifieds, speak to estate agents, etc. Then you get an idea of what houses cost in different sizes and in different areas. At this point you have been conditioned into accepting the value of houses (as set by who? Estate agents? The market? The builders?) You then find something you can afford, negotiate a little, and buy. You have accepted the misnumber they call price. Why is this a misnumber? The idea that a house can have the same value to all people is rediculous - a family of four will value a bigger house more than a retired couple. "Fine", you say, "let the retired couple buy elsewhere!". Well, let's extend the thought experiment a little - imagine that money was taken out of the equation and everyone worked on a barter system. Your circumstances changed and you now have a bigger family and you want to move closer to work and schools. Similarily, a couple near the CBD have retired and want to move out into quieter, safer suburbs. So the two parties decide to swop houses, because they both value the other's property more than their own. Having taken money out of the equeation, the misnumber is gone, and both parties win.
It gets worse though. What money is doing is getting people to trade objects (or services) for an intermediate trading object (currency), then trade that into another object (or service). That would not be so bad, except that the intermediate trading object changes it's intrinsic value over time as well! Just how bad the monetary system is, is a topic for another blog post, but I'd like to mention Zeitgeist The Movie (and it's Addendum) as must-watch free movies, and there are some good online resources for learning about the monetary system, such as this crash course
Recognising misnumbers is a truly empowering experience, as it fights that consumerism urge that is programmed into us from the day we are born. It helps to have technical knowledge in order to recognise some of these misnumbers, but in these days a Google search can be just as empowering.