One standard deviation has a 68% probability and two standard deviations have a 95% probability.
Radiocarbon dating has had an enormous impact on archaeology around the world since it made it possible to date carbon and wood could be directly without dependence on characteristic artifacts or written historical records.
Renfrew (1973) called it 'the radiocarbon revolution' in describing its impact upon the human sciences.
Oakley (1979) suggested its development meant an almost complete re-writing of the evolution and cultural emergence of the human species.
Each radiocarbon date has a statistical probability shown by the ± number.
This number is called a standard deviation and is a measure of the spread of measurements around the mean (average).
Desmond Clark (1979) wrote that were it not for radiocarbon dating, "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation" (Clark, 1979:7).
The Bristlecone pine trees in the Sierra Nevada mountains made this possible and today there are international tree ring databases and agreed-upon calibration curves. Libby later received the Nobel Prize in Chemistry in 1960: (From Taylor, 1987).Today, there are over 130 radiocarbon dating laboratories around the world producing radiocarbon assays for the scientific community."Everything which has come down to us from heathendom is wrapped in a thick fog; it belongs to a space of time we cannot measure.We know that it is older than Christendom, but whether by a couple of years or a couple of centuries, or even by more than a millenium, we can do no more than guess." [Rasmus Nyerup, (Danish antiquarian), 1802 (in Trigger, 19)].