However, the methods must be used with care -- and one should be cautious about investing much confidence in the resulting age...
There is no good way to tell how close the computed result is likely to be to the actual age.
There are minor differences between isotopes of the same element, and in relatively rare circumstances it is possible to obtain some amount of differentiation between them. The effect is almost always a very small departure from homogeneous distribution of the isotopes -- perhaps enough to introduce an error of 0.002 half-lives in a non-isochron age. but it is rare and the effect is not large enough to account for extremely old ages on supposedly young formations.) as minerals form.
This results in a range of X-values for the data points representing individual minerals.
The wonderful property of isochron methods is: if one of these requirements is violated, it is nearly certain that the data will indicate the problem by failure to plot on a line.
(This topic will be discussed in much more detail below.) Where the simple methods will produce an incorrect age, isochron methods will generally indicate the unsuitability of the object for dating.
Unfortunately, one must wade through some hefty math in order to understand the procedures used to fit isochron lines to data.