4. Second-class risk

4.1 The two risks of error

So far, we have considered a risk of error, i.e. a risk α of making an erroneous decision, which now needs to be explained in more detail. Vis-à-vis a hypothesis H ₀ , for example the null hypothesis, α is the risk of rejecting the hypothesis H ₀ when it is in fact correct. Typically, this is the supplier's risk. If we call H ₀ the hypothesis that a manufacture is acceptable, this is the risk of making the decision to consider as unacceptable a batch that is in reality acceptable.

But we must also consider the other way of being wrong: this is the β risk of not rejecting the H _...