=+1989: 81–89). The height from which the ball is dropped is determined so that there is a 50% chance of breaking through the glass. A breakthrough is considered to be a failure, whereas a ball that is stopped by the glass (even if the glass cracks) is considered to be a success. Suppose that 100 sheets of safety glass are randomly selected and tested, and that no change has been made in the resin used to manufacture the glass.