Answer to Question #132905 in General Chemistry for Mel

Question

What is the difference between accuracy and precision?

Answer 1

Accuracy describes how close the measured value is to the true value.

Precision describes the consistency of results of repeated measurements.

For example, it can be demonstrated using a thermometer. Let us assume the actual outside temperature of 80^oF.

• If during several measurements the thermometer registers 78.1, 81.9, 80.6, 79.5, it means that the thermometer is accurate but not precise because the average value is close to the true value, but results differ a lot from each other (are not consistent).
• If during several measurements the thermometer registers 83.0, 83.0, 82.9, 83.0, it means that the thermometer is precise but not accurate because the results are very close to each other but quite far from the true value.
• If during several measurements the thermometer registers 80.0, 80.1, 80.0, 79.9, it means that the thermometer is precise and accurate because the results are very close to each other and very close to the true value.