How should you report uncertainty for a calibrated pipet?

Always report a calibrated pipet’s measured volume together with its uncertainty, using either the manufacturer’s stated tolerance or the standard deviation from repeated measurements, and give the value with appropriate significant figures and a plus-minus uncertainty, for example twenty-five point zero zero plus-minus zero point zero one milliliters.

Think of the pipet like a ruler for liquids that can be a little bit off, so you tell people not just how much you measured but how sure you are about that number. If the manufacturer gives a tolerance, that tells you the usual error range for the pipet; if you make several measurements yourself, you can calculate the standard deviation to see how much the readings vary. You should round the uncertainty to one or two significant figures and then round the measured value to the same decimal place so they match neatly. Always include units and the plus-minus sign so anyone reading your result knows the size of the possible error.

Students often forget to match significant figures between the uncertainty and the reported value, which can make the result look inconsistent, so always round the measured number to the same decimal place as the uncertainty. Another common mistake is ignoring the manufacturer’s tolerance and reporting only a single measurement without an uncertainty, which gives a false sense of precision; instead, use the stated tolerance or repeat measurements to estimate uncertainty. Sometimes people report too many decimal places for a device that is not that precise, so keep the digits realistic to the pipet’s capability.

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Report Uncertainty for a Calibrated Pipet

1. Tell value and uncertainty together
2. Use manufacturer tolerance if available
3. Or calculate standard deviation from repeats
4. Round uncertainty to one or two figures
5. Match measured value decimal place

Common Mistakes Reporting Pipet Uncertainty

1. Mismatched significant figures between value and uncertainty
2. Reporting single measurement without uncertainty
3. Using too many decimal places

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