Question

You are in the laboratory and your instructor asks you to measure the volume of an aliquot of water (an aliquot is a scientific term that means a portion). Your instructor knows that this aliquot is exactly 275 mL. You take seven measurements: 150 mL, 300 mL, 500 mL, 275 mL, 543 mL, 100 mL, and 600 mL. Are your data accurate? Are they precise? Both? Neither? Explain using the definitions of accuracy and precision. (8 points)

Answer 1

Accuracy is a measure of how close you are to the true value of what is measured. Here the accurate measurement would be 275 ml as it is the true value.

Precision is how close your various measurements are relative to each other. A truly precise measurement would yield the same readings for all your trials. In this case, an accurate and precise measurement would give 275 ml for all readings. Since this is not the case for either, your measurements are neither accurate nor precise.