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Published byAudra Gardner Modified over 8 years ago

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Section 2.3 Measurement Reliability

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Accuracy Term used with uncertainties Measure of how closely individual measurements agree with the correct or true value

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Precision Term used for describing uncertainties Measures how closely individual measurements agree with one another

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Measurements can be precise while still being inaccurate.

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Percent Error Percent of the accepted value an error represents Ratio of an error to an accepted value Percent Error = error x 100 accepted value

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Significant Figures

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Measured quantities are generally reported in such a way that only the last digit is uncertain. Think of a thermometer All digits, including the last one, are considered significant figures

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Rules for Sig Figs All nonzero digits are significant Zeros between nonzero digits are significant 203 has 3 sig figs Zeros at the beginning of a number are never sig figs 0.0006 has 1 sig fig Zeros at the end of a number are significant if the number contains a decimal point 0.0300 has 3 sig figs 200 has 1 sig fig

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Sig Figs in Calculations Least certain measurement limits certainty of final answer!! RULE 1: In multiplication and division- sig figs of the answer should be the same as the measurement with the fewest sig figs 6.221cm x 5.2cm = 32.3492 cm 2 = 32 cm 2

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RULE 2: For addition and subtraction- final answer has the same number of decimal places as the measurement with the fewest decimal places. 20.42 + 1.322 + 83.1 = 104.842 = 104.8

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Intermediate Answers Retain at least one additional digit past the sig figs If using a calculator, enter numbers one after another

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