Final answer:
True
Thoroughly remixing composite samples before tests is true to ensure accurate and representative results.
Step-by-step explanation:
The statement that portions of a composite sample should be thoroughly remixed before beginning tests on the sample is True.
Thoroughly remixing the composite sample ensures that the components are mixed uniformly and any variations in the sample are accounted for. This helps in obtaining accurate and representative test results.
For example, if a composite sample consists of iron filings and flour, thorough remixing would help ensure that there are no areas in the sample where there are more iron filings or more flour, thus avoiding any bias in the test results.