In critical cases it is best to maintain a healthy skepticism until all possible checks of consistency have been made and two or more independent methods have produced the same result. Radioactive dating is usually considered most accurate if the age of the sample is not too much different than the half-life of the isotope used, although in favorable cases the age of the sample could be as much as 100 time less than the half-life or 10 times more.
The appropriateness of a particular isotope also depends on the mineralogy and history of the sample, so not all samples can be dated.
Suppose we have a tank partly filled with water, and a hole in the bottom through which the water is leaking out of the tank.
There are a number of assumptions involved, but if they all hold, when the ratio of Pb for the various samples, the points should lie on a straight line.Radioactive dating is the procedure of calculating an age for an artifact by determining how much of the radioactive material has decayed and calculating how long that would take given the half-life (how long it takes for half the material to decay) of the material being tested.Several dozen methods exist, using different radioactive isotopes and decay products, with varied dating ranges and precision.Sometimes a hypothesis must be made that may be plausible but has not been proven.At other times an additional measurement can eliminate the need for one assumption, although no science can be done without assumptions at some level.
As uranium decays to two different isotopes of lead at different rates of decay, two clocks are inherently built into the system.