In audit, we set 3 levels of materiality thresholds, Materiality, M Performance materiality, PM Tolerable misstatement, TM (Clearly trivial, CT)

Is the TM applied to each sample? or applied to the overall assertion?

I have seen both cases, meaning the TM is applied to each sample, and also the overall assertion (after compiling the projected misstatements)

In once case, TM is applied at a sample level, meaning it is applied to each sample/transaction. In the other case, TM is applied to the overall assertion.

If TM is applied at a sample level, you just compare the TM and the variance in each sample.

If TM is applied to the overall assertion, you compare TM and the projected misstatement amount.

My teacher says both ways are possible, but why? When do you use each way?