ABSTRACT
The measurement of physical entities such as length, volume, weight, electromagnetic radiation, and time involves uncertainties that cannot be eliminated entirely, but when recognized can be reduced to tolerable limits by meticulous attention to detail and close control of the significant variables. In addition errors, often unrecognized, are introduced by undesirable physical or chemical effects and by interferences in chemical reaction systems. In many cases, absolute values are not directly attainable, and therefore standards from which the desired result can be derived by comparison must be established. Errors are inherent in the measurement system. Although the uncertainties cannot be reduced to zero, methods are available by which reliable estimates of the probable true value and of the range of measurement error can be made.
