Hypothesis testing

At here we are talking about the probability of error. But it is quite unclear. And when we applying it on different data sets, so why the probability of error is increasing. So I wanna ask more about the probability of error.
https://www.codecademy.com/paths/data-science/tracks/scipy/modules/ae9ebd4a516dd08c736d5888f8780469/lessons/hypothesis-testing/exercises/multiple-t-tests

@script8482576949,

Welcome to the forums!

Have you had a chance to look at my response to a similar question here? I think it might provide some clarification on the subject. If after reading that thread you have a more specific question about hypothesis testing, feel free to ask it here in the forums!