Uncertainty, Precision, and Error in Experimental Results Uncertainty, Precision, and Error in Experimental Results Measurement of quantities such as length, volume, mass, temperature, light absorbance, and time is the heart of experimental science. Ultimately, the most elegant theory rests on numbers obtained in the laboratory by a scientist using a measuring device or instrument. For example, the mass of a sample obtained using a balance which weighs to the nearest 0.1 g may be 32.0 g. The uncertainty in this number is 1 unit in the tenths decimal place, and indicates that the balance reading is uncertain by 1 unit in this place. The mass is reported as 32.0 0.1 g, and the result of the weighing is known to 1 part in 320.
Scientists sometimes communicate uncertainty implicitly rather than explicitly.
For example, the mass above might be reported as 32.0 g. Now the uncertainty is 1 in the ten-thousandths place, and the mass is known to 6 significant figures. The result of this weighing is known to 1 part in about 320000, much better than with the less sensitive balance. Most quantities can be expressed in more than one system of units. Generally, uncertainties are related by the same conversion factors as relate the quantities in two scales.