Lesson 6: Precision

Often, many people don't know that a single number not only descibes a quantity, but also the amount of precision which it is associated with. the number 200 is less precise than the number 200.0 You might be asking yourself why the same two numbers can have different precisions but the answer lies in where the decimal is placed and how many numbers are around it.

Lets first look at the number 200. (period, not a decimal) It is relatively uncertain because there is no decimal place. 200 could have been 249 so the person making the measurement could have just rounded it down or the number could have been 150 and the person making the measurement could have rounded it up. So, 200 is only accurate only to the hundred digit.

200.0 on the other hand is more precise because the decimal after the zero indicates that the number was not rounded in the hundreds digit. However, there could still likely be some rounding going on in this figure. However, due to the decimal place and the zero to the right of it, we know the rounding occured in the tenths place. The number could have been 200.04 or 199.95.

This is a particularly useful aspect to remember about measurements, especially in the modern world. Precision applies to almost every field. It is seen frequently in the news or in arguemental literature. So, when you are given a figure or measurement, take a moment to think about how precise the figure is and how significantly it could have been rounded.