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If you read scientific reports closely, you will come across words such as error and uncertainty. What do they mean?

If a teacher tells you that you made an error on a test, then you got something wrong. In everyday language, that’s what error often means – a mistake.

In science, the word error means something slightly different. These errors aren’t mistakes. They indicate how far measurements are from their true values.

Grab a ruler and a pen. Measure the pen’s length. Give the pen and ruler to some friends and ask them to measure the pen’s length. Some people might give identical answers, while some might give slightly different answers.

So who is right? No one is completely right. The true length of the pen will be close to the average of all the answers. The disagreement reflects the fact that there is an uncertainty in the measurements. It is impossible to measure many quantities, including length, mass and time, with 100% certainty.

When scientists say that there are errors in measurements, they are acknowledging that there are always uncertainties in measurements. When they include an estimate of the uncertainty, they are identifying a range of values where the true value lies.

It is possible to reduce uncertainty. Lower uncertainties help create stronger scientific arguments and conclusions. A relatively low uncertainty means a scientist can be more confident that their conclusions reflect what is actually going on.

There are a number of ways to increase confidence in measurements. One way is to use more accurate equipment. For example, using a digital thermometer might remove errors caused by humans reading a traditional thermometer incorrectly. Another way is to repeat measurements and take an average, which can reduce the uncertainty.

So if you hear scientists talking about errors and uncertainties in their results, they aren’t saying their results contain mistakes. They are discussing some of the practical limitations of conducting experiments.

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