Accuracy and Precision

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Presentation transcript:

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. Instrument error is due to poorly calibrated or damaged instruments Human error includes mistakes in reading or recording measurements.

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.

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

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

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

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

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

How Many Significant Figures? 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.

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.

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

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.

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.