Final answer:
The absolute uncertainty increases when two measurements are added or subtracted. The uncertainty is tied to the accuracy and precision of the measuring device, and higher precision or accuracy typically means reduced uncertainty.
Step-by-step explanation:
When you add or subtract two measurements, the absolute uncertainty increases. If we have two separate mass measurements, such as 16.7 g with an uncertainty to the tenths place, and 5.24 g with an uncertainty to the hundredths place, you would add the absolute uncertainties. The total uncertainty in the sum or difference of the measurements reflects the compound uncertainty of both individual measurements.
The uncertainty of a measurement relates to the accuracy and precision of the measuring device. Accuracy refers to how close a measured value is to the true value, while precision refers to the repeatability of measurements, or how closely multiple measurements of the same quantity agree with each other. High precision can occur with low accuracy if measurements are consistent but far from the true value, as illustrated by dots that are close together but far from the target location.
In terms of a measuring system, a decrease in precision or accuracy leads to increased uncertainty. However, an increase in precision or accuracy generally means a reduction in uncertainty, making the measured values more reliable.