In reporting and reading measured values, precision is communicated using significant digits. Engineers and scientists are careful no to under or overstate the precision. Determining the number of significant digits is simple when numbers reported in scientific and engineering notation. The answer is to count the digits in the mantissa. For the U. S. standard decimal notation, the situation is quite different. A set of rules must be invoked as follows:
|
Rule |
Value | Significant Digits |
|
All non-zero digits are significant.
|
12.65 0.0364 |
4 3 |
|
Zeros between non-zero digits are significant
|
120.05 12,003.01 |
5 7 |
|
Place holding zeros are not significant including
|
0.0012 112,300 112.30.103 |
2 4 or 5 or 6 (ambiguous) 5 (not anymore!) |
|
Zeros to the right of the decimal and to the right of non-zero digits are
significant.
|
0.0120 45.0 |
3 3 (special case) |