Loading Psychology Significant Figures and Standard Form…
Quick guide: plain English, key facts and method
In plain English: Significant figures are the digits that carry meaning in a number. Standard form is a short way to write very large or very small numbers.
Key facts
- Start counting significant figures at the first non-zero digit.
- Leading zeros (0.00…) never count. Zeros between other digits always count.
- Zeros at the end, after a decimal point, do count: 3.00 has 3 s.f.
- Standard form is a × 10ⁿ, where a is at least 1 and less than 10.
- Numbers smaller than 1 have a negative power.
How to do it
- Count to the last digit you need to keep.
- Look at the next digit: 5 or more, round up. 4 or less, leave it.
- For large numbers, fill the gap with zeros: 23 456 to 2 s.f. is 23 000.
- For standard form, move the decimal point until one non-zero digit is in front of it. The number of moves is the power: moving the point left gives a positive power, moving it right gives a negative power.