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Accuracy and Precision

Accuracy and Precision. Why do we bother with significant figures, anyway?. Accuracy. Extent to which a reported measurement approaches the true value of the quantity measured Accuracy is affected by error : Method error occurs due to the method used.

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Accuracy and Precision

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  1. Accuracy and Precision Why do we bother with significant figures, anyway?

  2. Accuracy • Extent to which a reported measurement approaches the true value of the quantity measured • Accuracy is affected by error: • Method erroroccurs due to the method used. • Instrument error is due to poorly calibrated or damaged instruments • Human error includes mistakes in reading or recording measurements.

  3. Precision • Degree of exactness or refinement in a measurement. • Precision can be affected by: • Limitations of the instrument. • Estimation skill of the person taking the measurement. • The degree of precision in a measurement is shown by using significant figures.

  4. How Many Significant Figures? 245 m 3 sig figs Rule: All non-zero digits are significant

  5. How Many Significant Figures? 1074 kg 4 sig figs Rule: zeros between non-zero digits are significant

  6. How Many Significant Figures? 0.00345 s 3 sig figs Rule: Zeros to the left of the first non-zero digit are NOT significant.

  7. How Many Significant Figures? 2.00345 s 6 sig figs Rule: Zeros between non-zero digits are significant.

  8. How Many Significant Figures? 0.275000 m 6 sig figs Rule: Zeros at the end of a measurement that are to the right of the decimal point are significant.

  9. How Many Significant Figures? 275 000 m 3 sig figs Rule: Zeros at the end of a measurement are NOT significant UNLESS you know that they were measured OR the decimal point makes them significant.

  10. How Many Significant Figures? 275 000. 6 sig figs Rule: Zeros at the end of a measurement are NOT significant UNLESS you know that they were measured OR the decimal point makes them significant.

  11. How Many Significant Figures? 20 students RULE: Counted quantities and quantities that have no uncertainty do not involve significant figures.

  12. How Many Significant Figures? 375.4 m + 2.54 m = ? Answer = 377.9 m RULE: For addition and subtraction, the answer has the same precision as the measurement with the LEAST precision.

  13. How Many Significant Figures? (20.0 m)(3.0 m) = ? Answer = 60. m or 6.0 x 10 1 m RULE: For multiplication and division, the answer has the same number of significant figures as the measurement with the FEWEST significant figures.

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