In many cases, there are independent cues (such as geologic setting or the chemistry of the specimen) which can suggest that such assumptions are entirely reasonable.However, the methods must be used with care -- and one should be cautious about investing much confidence in the resulting age...especially in absence of cross-checks by different methods, or if presented without sufficient information to judge the context in which it was obtained.Isochron methods avoid the problems which can potentially result from both of the above assumptions.That encompasses the entire young-Earth timescale thousands of times over." in the decay equation.Age "uncertainty" When a "simple" dating method is performed, the result is a single number.This results in a range of X-values for the data points representing individual minerals.
Each such age would match the result given by the isochron.
The data points would be expected to start out on a line if certain initial conditions were met.
Consider some molten rock in which isotopes and elements are distributed in a reasonably homogeneous manner.
A routine statistical operation on the set of data yields both a slope of the best-fit line (an age) and a variance in the slope (an uncertainty in the age).
The better the fit of the data to the line, the lower the uncertainty.