An additional nice feature of isochron ages is that an "uncertainty" in the age is automatically computed from the fit of the data to a line.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).
In addition, it requires that these measurements be taken from several different objects which all formed at the same time from a common pool of materials.(Rocks which include several different minerals are excellent for this.) Each group of measurements is plotted as a data point on a graph.The X-axis of the graph is the ratio of in a closed system over time.The simplest form of isotopic age computation involves substituting three measurements into an equation of four variables, and solving for the fourth.The equation is the one which describes radioactive decay: If one of these assumptions has been violated, the simple computation above yields an incorrect age.
Age "uncertainty" When a "simple" dating method is performed, the result is a single number.