In this class, we have usually been satisfied if the relative uncertainty in our measurements was about =5%. This is really a fairly large uncertainty: but since our goal has been to understand physics concepts instead of rigorous quantitative experimentation= this has been good enough. However. in research settings it is important to be as precise as possible for the most stringent possible test of a tlteory. For example= the mass of a proton has been experimentally measured as Lassa: 153TBJ=DDDDUUUQDUller kg and the mass of a neutron has been measured as 1.57492T29310 l * l I)" kg. The uncertainties on these measurements are extremely small! Precise knowledge of the difference between the masses of protons and neutrons is crucial for studies of particle physics and atomic energy. A great deal of effort in research goes into making uncertainties as small as possible. The uncertainty budget can be helpful in minimizing uncertainty. Suppose that you are trying to design an experiment to make measurements as precisely as possible. You won't be able to design ways to minimize uncertainty if you donit know what factors might affect the uncertainty of your measurements. As you design, you might go through every item in the uncertainty budget, trying to nd ways to minimize the uncertainty in each item in the uncertainty budget. The total uncertainty of a measurand is determined by a sum of the uncertainties due to each item in the uncertainty budget. as shown in Measurement Corner #13. If one item in the uncertainty budget causes a much larger uncertainty than the other items in the uncertainty budget, the total uncertainty will be almost entirely due to the item with the largest uncertainty. While designing an experiment, a large improvement in the total uncertainty can be obtained by improving the uncertainty due to just the most troublesome item in the uncertainty budget. The uncertainty budget can show you where to focus efforts to improve your experiment. For example, in Measurement Corner :'13 we analyzed the uncertainty budget of a measurement of the period of a pendulum. The largest factor in the uncertainty budget was by far reaction time in using a stopwatch. If the experiment was redesigned so that the stopwatch was not used. the total uncertainty in the period could be decreased dramatically. This might be accomplished by switching to some type of electronic tinting system with an uncertainty of 001 s. The total uncertainty could be reduced from 0.119 s to [Limit s if the reaction time uncertainty was eliminated. The uncertainty budget can also be useful as you communicate your results to each other. On the lab reports in this class, you have been instructed to discuss the uncertainty in your measurements. What is meant by this is to discuss the uncertainty budget. For example, you should discuss what factors contribute to your uncertainty and why and estimate the uncertainty on your measurements