What aspect of sterilization is assessed using a biological indicator?

The correct answer focuses on the efficacy of the sterilization process. A biological indicator is a crucial tool used in assessing whether sterilization has been effectively achieved. It involves the use of specific microorganisms that are resistant to the sterilization methods applied, such as steam, ethylene oxide, or dry heat. After the sterilization cycle, the biological indicator is incubated to check for growth of the microorganisms.

If the microorganisms are killed, it indicates that the sterilization was effective; if they grow, it signifies that the process was not adequate. This method provides a direct measure of the sterilization process's ability to eliminate all viable forms of the particular microorganisms used in the indicator, thereby confirming the reliability of the sterilization method employed.

The other options pertain to different factors that, while important, do not directly measure the effectiveness of the sterilization process itself. For instance, cost-effectiveness refers to the economic consideration of sterilization practices, speed relates to how quickly the sterilization process can be completed, and personnel training is about the education and skills of the staff performing the sterilization. None of these address the biological confirmation of successful sterilization, which is the main purpose of using a biological indicator.