This particular resource used the following sources:. Skip to main content. Introduction to Chemistry. Search for:. Accuracy, Precision, and Error. Learning Objective Describe the difference between accuracy and precision, and identify sources of error in measurement. Precision expresses the degree of reproducibility or agreement between repeated measurements. The more measurements you make and the better the precision, the smaller the error will be. Show Sources Boundless vets and curates high-quality, openly licensed content from around the Internet.
Licenses and Attributions. Accuracy can be determined by one measurement while many measurements are needed to assess precision. For instance, by looking at the image above, just by one bullet fired, one knows if it is accurate or not, but a number of attempts have to be fired to tell if the result is precise.
Bullets that hit closer to the bullseye are considered more accurate. If a large number of bullets are fired, precision would be the size of the bullet cluster and not how close they are to the bullseye. In short, we can say that we want all our estimates to hit the target first be accurate to within a certain limit , and then we can concentrate on the precision afterward.
The more you work with a specific client, execute on individual projects, and have well defined the tasks, the more precise your scope becomes. In this sense, it is a goal to strive to achieve accuracy as soon as possible, and over time develop precision to scoping your projects.
I hope this has clarified how to use the two terms properly and as always, feel free to contact us for more information. Add some rocket fuel to your projects. Resource Management Manage your bandwidth. Project Management Run successful projects. Team Collaboration Enhance teamwork.
Project Accounting Keep the budget insight. By Industry Agency Scale sustainability. Consulting Organize work. Software Streamline delivery. By Team Operations Refine processes. Accuracy is a measure of how close a measurement is to the correct or accepted value of the quantity being measured. Precision is a measure of how close a series of measurements are to one another.
Precise measurements are highly reproducible, even if the measurements are not near the correct value. Darts thrown at a dartboard are helpful in illustrating accuracy and precision.
The distribution of darts on a dartboard shows the difference between accuracy and precision. Assume that three darts are thrown at the dartboard, with the bulls-eye representing the true, or accepted, value of what is being measured.
A dart that hits the bulls-eye is highly accurate, whereas a dart that lands far away from the bulls-eye displays poor accuracy. The figure above demonstrates four possible outcomes:. Students in a chemistry lab are making careful measurements with a series of volumetric flasks. Accuracy and precision are critical in every experiment.
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