Radiometric dating and astronomical dating
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.
Unless these factors are known, the calculated dates will not be reliable.We could measure (a) how much water the tank holds, (b) how much is still in the tank, and (c) the rate at which it is leaking out.We can calculate the age of the hole by subtracting (b) from (a) to find out how much water has left the tank, and then dividing this by (c), the rate at which it is leaking out.For example, the geological formations and dates from surrounding features may suggest that the "true" date can only lie within a certain range.As another example, a date that is obviously wrong would confirm a strong belief in the fundamental unreliability of radioactive dating.As uranium decays to two different isotopes of lead at different rates of decay, two clocks are inherently built into the system.
If the two agree with each other, the confidence in the date will be high.
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.
Given the complexity of radioactive dating, confirmation bias can also be a problem.
This arises when the person performing the analysis has a strong expectation of what the result should be.
In either case, there will be a subjective tendency to accept the result, rather than performing additional checks that might reveal unsuspected problems.