23. The quality control department detected five defective books in a batch of 100 randomly selected books. Find the relative frequency of the appearance of defective books.
Solution. The relative frequency of event $\boldsymbol{A}$ (the appearance of defective books) is equal to the ratio of the number of trials in which event $A$ occurred to the total number of trials conducted: $W(A)=5 / 100=0.05$.