Rounding

Rounding - 0.002364(±0.000003[0.02500(±0.00005 a...

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7/12/09 8:25 AM Untitled Document Page 1 of 1 file:///Users/bonk/Desktop/Chem19709f/Rounding.html Rounding Numbers To Be Consistent with Their Uncertainties We often indicate the probable uncertainty associated with an experimental measurement by rounding the result so that it contains only significant figures. By definition, the significant figures in a number are all of the digits known with certainty plus the first uncertain digit. The corollary is the first uncertain figure of the answer is the last significant figure. Example: for the quotient in which the uncertainty is given as the absolute standard deviation,
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Unformatted text preview: 0.002364 (±0.000003)/[0.02500 ((±0.00005), a calculator gives 0.09456 with a standard deviation of 0.00022. Express the result with proper sig figs. The first uncertain digit in the calculated standard deviation occurs in the fourth decimal place making the fourth decimal place in the answer the last significant figure. The result is then 0.0946 ± 0.0002. (Skoog, Holler & Crouch, Principles of Instrumental Analysis, 6th, Thomson Brooks/Cole, Canada, 2007, 982) See additional examples on the next pages....
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