Final answer:
The statement by the patient indicating effective teaching on PCA use is their acknowledgment of reduced anxiety about overdosing, demonstrating an understanding of the device's safety features.
Step-by-step explanation:
The correct statement that indicates to the nurse that teaching on a patient-controlled analgesia (PCA) device has been effective is: "I feel less anxiety about the possibility of overdosing." PCA allows patients to self-administer a preset dose of pain medication when they experience pain, but the device is programmed to limit dosing intervals and prevent overdosing. This statement shows that the patient understands the safety features of the PCA and is comfortable using it without fear of taking too much medication.