Dr. williamson discovered that the latest depression instrument had a weak correlation when administered over time to the same patients. the test lacked:

The answer to this question would be precision

If the test has high precision, the result of the repeated test would have a close value together. In this case, the test is used repeatedly on the same patient but it has a weak correlation. That means the test is not precise, so the same condition did not give the same result. 

The answer is centrioles forming happens in animal cell mitosis but doesn't happen in plant cell mitosis.