Which term refers to the variability in measurements where there is an equal chance of getting a higher or lower reading each time?

The term that refers to the variability in measurements, where there is an equal chance of getting a higher or lower reading each time, is random uncertainty. Random uncertainty arises from inherent unpredictability in the measurement process, such as fluctuations in the environment or how an experiment is conducted. This type of uncertainty results in different readings for the same measurement, all of which may be equally likely to be above or below the actual value.

Random uncertainty can often be reduced by taking multiple measurements and calculating an average, as it encompasses variations that are not consistent and tend to cancel themselves out over several trials. In contrast, systematic error refers to consistent inaccuracies in measurements caused by flaws in the measurement system, such as calibration errors, while absolute and relative errors are measures of the accuracy of a measurement in terms of the difference from a true value or the proportion of that difference, respectively.