Four groups of scientists, in different parts of the world, are dating fossils found in a rock layer of the same geologic time period. to validate the age of their fossils, the results of their tests would need to be:

complex
identical
inconsistent
non-testable

The result should be identical.

Explanation:

As fossils gives us information about geological time period and also gives us information about the vegetation,types of animals or plants that were available at that time,their genetic information etc. If any fossils are found in a rock layer  of the same geological time,should be examined first and check whether they are identical or not.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.