An index generally refers to a quantity derived from a ratio of 2 (or more) measurable quantities and often is used to compare individuals with each other or with normal values. Except for products or quotients representing specific derived SI units of measure (see also , Expressing Unit Names and Symbols, Products and Quotients of Unit Symbols), the ratio of SI units used to create indexes does not represent an SI convention.At first mention in the text, the formula used to calculate the index should be described; thereafter, the numerical value for the index may be given without units attached ...
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