Nines (notation)

Nines are an informal logarithmic notation for proportions very near to one or, equivalently, percentages very near 100%. Put simply, "nines" are the number of consecutive nines in a percentage such as 99% (two nines)^[1] or a decimal fraction such as 0.999 (three nines). Their common uses include grading the purity of materials, or measuring the availability of a service.

^ Technical Information for Congress: Report to the Subcommittee on Science, Research and Development of the Committee on Science and Astronautics. 25 April 1969. p. 123. Retrieved 19 April 2024. For example, the difference between a purity of aluminum of "four nines" and "six nines" is understandable to a scientist, but not necessarily to a politician. (These are 99.99 percent pure and 99.9999 percent pure).

[congress-1] Technical Information for Congress: Report to the Subcommittee on Science, Research and Development of the Committee on Science and Astronautics. 25 April 1969. p. 123. Retrieved 19 April 2024. For example, the difference between a purity of aluminum of "four nines" and "six nines" is understandable to a scientist, but not necessarily to a politician. (These are 99.99 percent pure and 99.9999 percent pure).

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