Final answer:
A nurse teaching a breast self-examination class is an example of effectiveness, as it aims to produce the desired outcome of enabling early breast cancer detection.
Step-by-step explanation:
The action of a nurse conducting a class on breast self-examination for a group of 50 women best describes effectiveness. Effectiveness refers to the ability to produce a desired outcome or the ability to produce intended results. By teaching these women how to perform breast self-examinations, the nurse is effectively providing them with knowledge that can lead to early detection of breast cancer, which can be critically important for successful treatment and outcomes.