07-Error_2_web - Chemistry222 Fall2010...

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Chemistry 222 Fall 2010 STATISTICS, ANALYSIS OF  EXPERIMENTAL ERROR
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1. The mean value and standard deviation of the concentration of lead in drinking water is reported as 8.3354 ± 0.43689 ppb. Which expresses the value with the correct number of significant figures? (A)8 ppb (B) 8.3 ppb (C) 8.335 ppb (D) 8.3354 ppb The uncertainty is ± 1 in the last digit.
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2. Which is not a characteristic of random error? (A) It cannot be removed from the analysis (B) It fluctuates randomly around the mean value (C) It can be subtracted from both the standard and samples (D) It may be quantified by statistical parameters such as the standard deviation
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A result of chemical analysis consists of two elements: the   value   (x) and the   error  e   (or  s ).    x ±  e We will now estimate the explicit  error,   and study it.
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Example: A typical set of results of a mass measurement (in mg); sample size = 7: 24.9; 24.7; 23.2; 24.5; 25.1; 24.4; 24.3
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standard deviation exactly, we know only their estimates. This is because in practice we never deal with populations
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This note was uploaded on 12/28/2010 for the course CHEMISTRY 222 taught by Professor Wieckowski during the Spring '10 term at University of Illinois at Urbana–Champaign.

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07-Error_2_web - Chemistry222 Fall2010...

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