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

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
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
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
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.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

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.

Page1 / 7

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

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online