Final answer:
The best method to determine if the teaching on changing the central line dressing was effective is for the partner to demonstrate a dressing change themselves.
Step-by-step explanation:
The best method to determine if the teaching on changing the central line dressing was effective for the client's partner would be for the partner to demonstrate a dressing change themselves. This allows the nurse to assess if the partner can accurately perform the steps and ensure proper technique is used. The partner verbally stating the steps for changing the dressing is helpful, but it does not guarantee their ability to actually perform the procedure correctly. Observing the nurse or watching a video may provide some understanding, but hands-on practice is the most effective way to assess competence.