Mixing Studies: What Constitutes Correction?

This week George posts a new Quick Question to learn how we define PTT mixing study correction. Here is how the question will look:

When performing PTT mixing studies using normal control plasma (NP), what criterion do you use to define correction?
a. Mix result within 10% of NP result
b. Mix result within 5 seconds of NP result
c. Mix result within reference interval
d. Mix result within 5 seconds of reference interval mean
e. Other: Please post or email to [email protected]

There are more answers to this question than can efficiently fit into a multiple choice format, so please feel free to both vote in the right-hand column and respond in the comments section below with your approach, including your rationale and references. We will compile your responses and compare them with relevant comments from past Fritsma Factor entries. Thank you.