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Accuracy, Precision, and Significant Figures in Measurement. Accuracy is how close to the true value a given measurement is. Precision is how well a number of independent measurements agree with one another. Accuracy, Precision, and Significant Figures in Measurement.
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Accuracy, Precision, and Significant Figures in Measurement • Accuracyis how close to the true value a given measurement is. • Precisionis how well a number of independent measurements agree with one another.
Accuracy, Precision, and Significant Figures in Measurement • Significant Figures are the total number of digits in the measurement. • The results of calculations are only as reliable as the least precise measurement. • Rules exist to govern the use of significant figures after the measurements have been made.
Accuracy, Precision, and Significant Figures in Measurement • Rules for Significant Figures: • Zeros in the middle of a number are significant • Zeros at the beginning of a number are not significant • Zeros at the end of a number and following a period are significant • Zeros at the end of a number and before a period may or may not be significant.
Accuracy, Precision, and Significant Figures in Measurement • Rules for Rounding Numbers: • If the first digit removed is less than 5 - round down • If the first digit removed is greater than 5 - round up • If the first digit removed is 5 and following numbers are nonzero - round up • If the first digit removed is 5 and following numbers are zero - round down
Accuracy, Precision, and Significant Figures in Measurement • How many significant figures does each of the following measurements have? • (a) 0.036653 m (b) 7.2100 x 10–3 g • (c) 72,100 km (d) $25.03
Accuracy, Precision, and Significant Figures in Measurement • How many significant figures does each of the following measurements have? • (a) 0.036653 m (5) (b) 7.2100 x 10–3 g (5) • (c) 72,100 km (3 or 4 or 5) (d) $25.03 (exact)
Accuracy, Precision, and Significant Figures in Measurement • Round off each of the following measurements. • (a) 3.774499 L to four significant figures • (b) 255.0974 K to three significant figures • (c) 55.265 kg to four significant figures
Accuracy, Precision, and Significant Figures in Measurement • Round off each of the following measurements. • (a) 3.774 L • (b) 255 K • (c) 55.26 kg
Accuracy, Precision, and Significant Figures in Measurement • Rules for Calculating Numbers: • During multiplication or division, the answer can’t have more sig figs than any of the original numbers. • During addition or subtraction, the answer can’t have more digits to the right of the decimal point than any of the original numbers.
Significant Figure Calculations Ok, now… Try These!