PHY 1321 Lecture Notes - Lecture 1: Observational Error, Error Bar, Measuring Instrument

• School: University of Ottawa
• Department: Physics
• Course: PHY 1321
• Professor: Andrzej Czajkowski

Document Summary

In ordinary conversation we tend to use the terms accuracy and precision interchangeably, but in the context of scientific measurement, they give very different meanings. They are actually two different ways of expressing the uncertainty of experimental data. Accuracy: refers how closely a measured value of a quantity corresponds to its true value. Precision: expresses the degree of reproducibility of a result when the experiment is repeated under the same conditions. In other words precision refers to how closely individual measurements agree with each other. A result can be measured precisely yet still be inaccurate. In order to better understand the difference between accuracy and precision, let us take the example of an archer shooting a total of thirteen arrows at a target. From the archer"s first results (shown in figure 1a), we can conclude that on average the archer is accurate but no precise since all the arrows have a large deviation with respect to each other.