Достовірність

Accuracy and Precision

When taking measurements of anything there can be some measurement uncertainty due to limitations of the measuring instrument, random error, observational error, or human error. We aim to avoid systematic error in science because that would mean there is a recurring issue causing error that must be fixed. There are 2 terms used to describe the amount of uncertainty in a measurement.

• Accuracy: the closeness of a measured value to the true value

• Precision: the closeness of different measured values to each other

Ideally, measurements would be both precise and accurate, but that is not always the case.

Comparison Example

Imagine you measure the mass of a metal sphere with a true mass of 15.000g. If three measurements are taken the possible options are:

• Accurate and precise: average of measurements is close to true mass and the measurements are all approximately the same

• Average: 15.001g, measurements: 15.000g, 15.001g, 15.001g

• Accurate and not precise: average of measurements is close to true mass, but measurements are not close together

• Average: 15.001g, measurements: 15.811g, 14.301g, 14.891g

• Not accurate and precise: average of measurements is not close to true mass, but measurements are close to each other

• Average: 15.827g, measurements: 15.826g, 15.8297g, 15.825g

• Not accurate and not precise: average of measurements is not close to true mass and measurements are not close to each other

• Average: 15.289g, measurements: 16.020g, 15.324g, 14.523g

Precision refers to the closeness of two or more measurements. The results of an experiment can be precise even if the results are not close to the wanted values, as long as the results are similar to one another.

Accuracy refers to how close a result is to the true, or known value. To measure this during an experiment, you compare a particular result to the wanted value, not the other measurements.

(Video) Accuracy and Precision | It's Easy!

by 2 Minute Classroom

This video by 2 Minute Classroom will teach you all you need to know about accuracy and precision, all in just two minutes! You'll learn how the terms are different, and then you'll see some examples of what they look like using targets.