Precise values differ from each other because of random error, which is a form of observational error. You can think of accuracy and precision in terms of a basketball player.
If the player always makes a basket, even though he strikes different portions of the rim, he has a high degree of accuracy. If he doesn't make many baskets but always strikes the same portion of the rim, he has a high degree of precision.
A player whose free throws always make the basket the exact same way has a high degree of both accuracy and precision. Take experimental measurements for another example of precision and accuracy. You can tell how close a set of measurements are to a true value by averaging them. If you take measurements of the mass of a The average of your measurements is Yet, your measurements were consistent.
If your scale gives you values of The average of the measurements is The more precise scale would be better to use in the lab, providing you made an adjustment for its error. In other words, it's better to calibrate a precise instrument than to use an imprecise, yet accurate one. An easy way to remember the difference between accuracy and precision is:. Do you think it's better to use an instrument that records accurate measurements or one that records precise measurements?
If you weigh yourself on a scale three times and each time the number is different, yet it's close to your true weight, the scale is accurate. Yet it might be better to use a scale that is precise, even if it is not accurate. In this case, all the measurements would be very close to each other and "off" from the true value by about the same amount.
A classic way of demonstrating the difference between precision and accuracy is with a dartboard. Think of the bulls-eye center of a dartboard as the true value. The closer darts land to the bulls-eye, the more accurate they are.
Question Set:. An oceanographer needs to go out in a boat to collect an important temperature and salinity data logger that is attached to an underwater buoy. How does each of the following situations illustrate the differences between precision and accuracy?
The oceanographer checks the weather forecast the night before her trip so she knows what to wear on the boat. The other GPS units belonging to her colleagues on the boat also indicate that they are at the correct location.
After an extensive search, the oceanographer finds the buoy 50 meters m from the boat. While on the way back to shore, the oceanographer throws in a fishing line to see if she can catch anything for dinner. The one learning a language! Learn about premium features. Tired of searching? HiNative can help you find that answer you're looking for. Register for free. Solve your problems more easily with the app! Repeatability : The variation observed when the same operator measures the same part repeatedly with the same device.
Reproducibility : The variation observed when different operators measure the same part using the same device. A dart board can help us visualize the difference between the two concepts:. Accurate and Precise Precise Accurate, but not Precise Neither Accurate nor Precise. Maybe this example can help to further show the differences.
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