Inspection Plan with Wrong Detection

In a document in Research Gate (about Inspection) I read the following formula, about a random variable X:

• the mean value E(X)=p*beta,

where

1.    “p is the probability that a product is REALLY defective”

2.    “alfa is the probability that a product REALLY NON_defective is WRONGLY detected as defective”

3.    “beta is the probability that a product REALLY defective is WRONGLY detected as NON_defective”

In my opinion, E(X) cannot be the above formula.

What do the iSixSigma experts think?

THANKS in advance.