Final answer:
A measured property may not accurately indicate the target property due to external factors, measurement errors, or changes in the object's physical properties not associated with its chemical composition.
Step-by-step explanation:
The measured property may not be a good indicator of the target property when there is a discrepancy due to external factors, measurement errors, or irregularities in the object being measured. For example, when calculating the average speed of an athlete, the time taken and distance covered are measured. However, factors like wind resistance, variations in the athlete's pace throughout the sprint, or inaccuracies in the timekeeping device can lead to a speed calculation that does not accurately reflect the athlete's typical performance. The accuracy of the measured property as an indicator of the target property also decreases if there is a change in the physical property of the object that is not related to its chemical composition, such as when temperature affects the measurement of length due to thermal expansion.