What is the difference between precision and accuracy?

What is the difference between precision and accuracy?

• A. Precision is the consistency of results; accuracy is how close results are to the true value.
• B. Precision measures bias; accuracy measures variability.
• C. Precision is about units; accuracy is about scale.
• D. Precision equals accuracy in ideal conditions.

Answer: (B)

Precision is about how consistently you get the same result when you repeat measurements. If the results cluster tightly, you have high precision. Accuracy is about how close those results are to the true value. If the measurements average near the true value, you’re accurate. You can be precise but not accurate if your results are very consistent but off from the true value (a systematic error shifts everything). You can be accurate but not precise if your results are scattered but average to the true value. The statement that swaps these ideas—saying precision measures bias and accuracy measures variability—confuses systematic error (bias) with spread (variability). Other options bring in units or claim they always align in ideal conditions, which isn’t the general relationship between precision and accuracy.

Precision is about how consistently you get the same result when you repeat measurements. If the results cluster tightly, you have high precision. Accuracy is about how close those results are to the true value. If the measurements average near the true value, you’re accurate.

You can be precise but not accurate if your results are very consistent but off from the true value (a systematic error shifts everything). You can be accurate but not precise if your results are scattered but average to the true value.

The statement that swaps these ideas—saying precision measures bias and accuracy measures variability—confuses systematic error (bias) with spread (variability). Other options bring in units or claim they always align in ideal conditions, which isn’t the general relationship between precision and accuracy.