Box 3-1 What Are Standard Reference Materials

Inaccurate laboratory measurements can mean wrong medical diagnosis and treatment, lost production time, wasted energy and materials, manufacturing rejects, and product liability. To minimize errors, the U.S. National Institute of Standards and Technology and institutes of standards of other nations distribute standard reference materials, such as metals, chemicals, rubber, plastics, engineering materials, radioactive substances, and environmental and clinical standards that can be used to test the accuracy of analytical procedures. 

For example, in treating patients with epilepsy, physicians depend on laboratory tests to measure blood serum concentrations of anticonvulsant drugs. Low 

Before introduction of this reference material, five laboratories analyzing identical samples reported a range of results with relative errors of 40% to 110% of the expected value. After distribution of the reference material, the error was reduced to 20% to 40%. 

Ozone (O3) is a corrosive gas that harms your lungs and all forms of life. It is formed near the surface of the Earth by the action of sunlight on air pollutants largely derived from automobile exhaust. The U.S. Environmental Protection Agency sets an 8-h average O3 limit of 80 ppb (80 nL/L by volume) in air. 

Precision is a measure of the reproducibility of a result. Accuracy is how close a measured value is to the true value. 

---