RDGerroranal

# RDGerroranal - Reading Analysis of Errors Revised ANALYSIS OF ERRORS Precision and Accuracy Two terms are commonly associated with any discussion

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Reading: Analysis of Errors Revised 1/21/10 1 ANALYSIS OF ERRORS Precision and Accuracy Two terms are commonly associated with any discussion of error: "precision" and "accuracy". Precision refers to the reproducibility of a measurement while accuracy is a measure of the closeness to true value. The concepts of precision and accuracy are demonstrated by the series of targets below. If the center of the target is the "true value", then A is neither precise nor accurate. Target B is very precise (reproducible) but not accurate. The average of target C's marks give an accurate result but precision is poor. Target D demonstrates both precision and accuracy - which is the goal in lab. A B CD All experiments, no matter how meticulously planned and executed, have some degree of error or uncertainty. In general chemistry lab, you should learn how to identify, correct, or evaluate sources of error in an experiment and how to express the accuracy and precision of measurements when collecting data or reporting results. Errors Three general types of errors occur in lab measurements: random error, systematic error, and gross errors. Random (or indeterminate) errors are caused by uncontrollable fluctuations in variables that affect experimental results. For example, air fluctuations occurring as students open and close lab doors cause changes in pressure readings. A sufficient number of measurements result in

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Reading: Analysis of Errors Revised 1/21/10 2 evenly distributed data scattered around an average value or mean. This positive and negative scattering of data is characteristic of random errors. The estimated standard deviation (the error range for a data set) is often reported with measurements because random errors are difficult to eliminate. Also, a "best-fit line" is drawn through graphed data in order to "smooth out" random error. Systematic (or determinate) errors are instrumental, methodological, or personal mistakes causing "lopsided" data, which is consistently deviated in one direction from the true value.
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## This note was uploaded on 11/20/2010 for the course CHEMISTRY Chem 1LE taught by Professor Dr.kimberlyedwards during the Spring '10 term at UC Irvine.

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RDGerroranal - Reading Analysis of Errors Revised ANALYSIS OF ERRORS Precision and Accuracy Two terms are commonly associated with any discussion

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