Null Hypotheses Threshold question

Hi Matthew,

First and foremost, thank you so much for developing this program. It has helped me pass both CMT levels 1 and 2 already. The question I have pertains to the following slide:

CMT 3 > Part 3 Section 1: Risk Management > Lecture 10 > @ 35 minutes into the lecture

Before hypotheses testing, a threshold is determined for rejecting the Null Hypotheses. The threshold is determined prior to testing to avoid possible accusations of overfitting. My question is how do you determine the threshold without looking at the results? Is there a standard way of determining the threshold? For example: Anything above a P value of 0.10 disproves Null Hypotheses?