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Significant Figures/Accuracy and Precision

Significant Figures/Accuracy and Precision. Accuracy vs Precision. Accuracy = Precision =. How close you are to the correct answer. How close your answers are to each other. Percent Error. You can quantify how accurate you are by calculating the percent error of your measurement

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Significant Figures/Accuracy and Precision

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  1. Significant Figures/Accuracy and Precision

  2. Accuracy vs Precision Accuracy= Precision = How close you are to the correct answer How close your answers are to each other

  3. Percent Error You can quantify how accurate you are by calculating the percent error of your measurement Percent Error = Experimental Value – Accepted Value x 100 Accepted Value Absolute Value Sign – Make this value positive

  4. Example In the lab, you measure the mass of an object to be 3.56 g. The actual mass of the object is 4.23 g. What is the percent error? Percent Error = Experimental Value – Accepted Value x 100 Accepted Value Percent Error = 3.56g – 4.23g x 100 = 15.8% 4.23

  5. Measurement When you record a measurement, always record all certain digits PLUS one uncertain digit. These are called the significant figures (digits) of the measurement

  6. Measurement If the measurement lands on a line, the uncertain number is 0! 0.90 cm

  7. Sig Fig Rules Rules for Identifying Significant Figures (Sig Figs) (Found on your STAAR Reference Sheet) • Non-zero digits and zeros between non-zero digits are always significant. 145 (3 s.f.) , 2001 (4 s.f.) 2. Leading zeros are not significant. 0.00032 (2 s.f.) 3. Zeros to the right of all non-zero digits are only significant if a decimal point is shown. 3.400 (4 s.f.), 200 (1 s.f.)

  8. Practice! Determine the number of sig. figs. in the following numbers. 0.0032 2sf 2sf 3200 4sf 4sf 32.00 3002 32 2sf

  9. Mult./Div. Rules Rounding multiplication/division calculations to the proper number of sig figs Round the answer to the lowest number of sig figs in the calculation 23.0 x 2.003 x 0.245 = 11.286905 = 3sf 4sf 3sf 11.3 3 sf

  10. Practice! Perform the following calculations and round the answer to the proper number of sig figs. 450 = 3.947368421 = 114 84 x 31.221 = 2622.564 = 2 sf 2 sf 3.9 3 sf 2 sf 5 sf 2 sf 2600

  11. Add./Sub. Rules Rounding addition/subtraction calculations to the proper number of decimals Round the answer to the lowest number of decimals (dp) in the calculation 23.0 + 2.003 + 0.24 = 25.243 = 25.2 1 dp 2 dp 1 dp 3 dp

  12. Practice! Perform the following calculations and round the answer to the proper number of decimal places. 39.64 + 1.3 = 40.94 = 195.4 - 193 = 2.4 = 1 dp 2 dp 1 dp 40.9 0 dp 0 dp 1 dp 2

  13. Finished!

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