Chapter 5

# Chapter 5 - Chapter 5 Errors In Chemical Analyses Mean...

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Chapter 5 Errors In Chemical Analyses Mean , arithmetic mean , and average (x) are synonyms for the quantity obtained by dividing the sum of replicate measurements by the number of measurements in the set. where, x i represents the individual values of x making up a set of N replicate measurements. The median is the middle result when replicate data are arranged in order of size. Equal number of results are larger and smaller than the median. For an odd number of data points, the median can be evaluated directly. For an even number, the mean of the middle pair is used. x x N i i N = = 1

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Results from replicate determinations
Precision Precision is the closeness of results to others that have been obtained in exactly the same way. Precision describes the reproducibility of measurements. Precision of a measurement is determined by simply repeating the measurement on replicate samples. Three terms are widely used to describe the precision of a set of replicate data: standard deviation, variance, and coefficient of variation. All these terms are functions of the deviation from the mean d i or just the deviation. d i = | x i – x |

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Accuracy Accuracy is the closeness of a measurement to the true or accepted value and is expressed by the error. Accuracy measures agreement between a result and its true value but precision describe the agreement among several
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## This note was uploaded on 05/09/2010 for the course CHEM 3245 taught by Professor Anwara.bhuiyan during the Spring '10 term at Arkansas Tech.

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Chapter 5 - Chapter 5 Errors In Chemical Analyses Mean...

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