Both accuracy and precision are important to scientific measurement. I'll try to explain the difference with a couple of illustrations. I should start by saying, sometimes the Words are used interchangeably but they shouldn't be. I consider precision to mean resolution. That is how fine/small a reading you can get.
- Assume an electronic thermometer (digital display) can display answers to the nearest one hundredth of a degree. But, the thermometer isn't able to measure with that accurately. Maybe it's only accurate to the nearest whole degree. In this case the precision is greater than is supported by the accuracy of the device.
- Now take the opposite case where the thermometer is able to measure temperature accurately to one hundredth of a degree but the instrument can only display whole degrees. In this case the precision does not support the accuracy.
Ideally the accuracy and precision of an instrument are the same but often that's not the case.
