Dating age range graph
The pair of blue curves show the radiocarbon measurements on the tree rings (plus and minus one standard deviation) and the red curve on the left indicates the radiocarbon concentration in the sample.
It gives the time range, from which you can be 95% sure the sample came.Once calibrated a radiocarbon date should be expressed in terms of cal BC, cal AD or cal BP.The cal prefix indicates that the dates are the result of radiocarbon calibration using tree ring data.There are two main methods used for calculating age ranges from the calibration curve: The first method to be employed was called the `intercept method' because it can be done by drawing intercepts on a graph.
This method will tell you the years in which the radiocarbon concentration of tree rings is within two standard deviations of your measurement (e.g.
between 2940BP and 3060BP for the measurement 3000 -30BP).