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Samples older than this will typically be reported as having an infinite age.Some techniques have been developed to extend the range of dating further into the past, including isotopic enrichment, or large samples and very high precision counters.Even if the systematic errors are not corrected, the laboratory can estimate the magnitude of the effect and include this in the published error estimates for their results.The limit of measurability is approximately eight half-lives, or about 45,000 years.Different labs use this data in different ways; some simply average the values, while others consider the measurements made on the standard target as a series, and interpolate the readings that would have been measured during the sample run, if the standard had been measured at that time instead.The fraction modern is then converted to an age in "radiocarbon years", meaning that the calculation uses Libby's half-life of 5,568 years, not the more accurate modern value of 5,730 years, and that no calibration has been done: There are several possible sources of error in both the beta counting and AMS methods, although laboratories vary in how they report errors.

The usual presentation of a radiocarbon date, as a specific date plus or minus an error term, obscures the fact that the true age of the object being measured may lie outside the range of dates quoted.The resulting standard value, A The first standard, Oxalic Acid SRM 4990B, also referred to as HOx I, was a 1,000 lb batch of oxalic acid created in 1955 by the National Institute of Standards and Technology (NIST).Since it was created after the start of atomic testing, it incorporates bomb carbon, so measured activity is higher than the desired standard.In 1970, the British Museum radiocarbon laboratory ran weekly measurements on the same sample for six months.The results varied widely (though consistently with a normal distribution of errors in the measurements), and included multiple date ranges (of 1σ confidence) that did not overlap with each other.

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The extreme measurements included one with a maximum age of under 4,400 years, and another with a minimum age of over 4,500 years.