Significant Digits What are they? And How do you use them? Accuracy: This is the concept which deals with whether a measurement is correct when compared to the known value or standard for that particular measurement. When a statement about accuracy is made, it often involves a statement about percent error. Percent error is often expressed by the following equation: % error = (|experiment value - accepted value| / accepted value) x 100% Also see Problem Set # 1-14 in the workbook Precision: This is the concept which addresses the degree of exactness when expressing a particular measurement. The precision of any single measurement that is made by an observer is limited by how precise the tool (measuring instrument) is in terms of its smallest unit. How would you divide the following 1 meter long bar up into smaller divisions? Why? What would your choice have to do with precision? 1 METER BAR Precision and Measuring: Significant Digits: When someone else has made a measurement, you have no control over the choice of the measuring tool or the degree of precision associated with the device used. You must rely on a set of rules to tell you the degree of precision. Refer to the “Rules for determining when zeros are significant” (PS#1-9, workbook) Significant Digits in Math: Use PS#1-10 to check your understanding of identifying significant digits in measurements. See PS#1-11 for the rules about using significant digits in addition and subtraction. See PS#1-11 for the rules about using significant digits in multiplication and division. Then go on and do PS#1-12.
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