Sunday, February 20, 2011

Trade Off #18: Speed vs Accuracy

As you decrease the time in which you complete a task, you must give up some of the control which allows you to ensure that each part of the process goes as desired. This trade off between speed and accuracy is very widespread and is one of the most intuitive trade offs in the canon.

You can test yourself on this trade off by going to any typing test website and varying the speed with which you type. At more words per minute you will tend to have more misspelled words, while at fewer wpm you will have fewer misspelled words. Other examples:
  • Watson, the AI created by IBM to compete at Jeopardy, faces a speed vs accuracy trade-off in that the longer it has to search its databases and run its algorithms, the more confidently it can assign a high probability to one of its answers. (see here)
  • If you take longer to respond to emails, people will expect your responses to be more accurate, whereas if respond right away, their expectations will be much lower. This is because they intuitively recognize the trade off you face between speed and accuracy. (see here)
  • In the world memory championships, as contestants take longer to look at a card, their mental representation of it become richer, making subsequent recall more accurate. So they must race to make it interesting. (see here)
This trade-off seems to not apply everywhere, in that people's predictions about soccer games may actually decrease in accuracy with more conscious attention. But this is probably because people tend to over fit their models to the data with too much conscious processing, an example of the precision vs simplicity trade-off.

To say that there is a trade-off doesn't completely preclude free lunches. Ray Allen can shoot 3's more accurately than I can, and he can shoot them faster. The key is that if Allen were to shoot basketballs at 2x his own comfortable speed, he'd no doubt be less accurate. So, with respect to just this speed vs accuracy trade off, the amount he has practiced seems like a free lunch, but we know that once we consider other trade-offs, it is not.

(photo credit to flickr user Odd; the slower the sun sets, the more accurately you can predict the exact moment it will cross the horizon)