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Significant Figures. Always record data as accurately as you can (as many sig. figs. as method allows) The last digit of the value that you record should be estimated Do not round values until calculations are completed Examples Follow. Sig Figs Examples. Addition and Subtraction
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Significant Figures • Always record data as accurately as you can (as many sig. figs. as method allows) • The last digit of the value that you record should be estimated • Do not round values until calculations are completed • Examples Follow
Sig Figs Examples • Addition and Subtraction • Use least # of decimal places • 15.287+13.07= 28.36 • Multiplying and Dividing • Use least # of sig. figs. • 0.0387*1.0= 0.039 • (100.8+0.524)*10.05 = 4 sig figs • 100.8+0.524 = 101.3 • 101.3*10.05 = 1018
Relative & Absolute %Error • Precision Determination • How far are values off from each other • Standard Deviation OR • Relative % Error • = (largest – smallest)*100%/average • Accuracy Determination • How far off from real value? • Absolute %Error • = (|experimental value – real value|)*100%/real value
Standard Deviation • Error Analysis-how far the values differ from the averages (related to %relative error, precision) • Normal Distribution Assumed • AverageNormal • S= ((xi-x)2)/(N-1) • Give values as Average ± Std Dev