Precision vs. Accuracy: Understanding the Difference in Measurements, Lecture notes of Chemistry

Download Precision vs. Accuracy: Understanding the Difference in Measurements and more Lecture notes Chemistry in PDF only on Docsity! Most people think precision and accuracy are the same thing. Technically, they’re not. Do you know the difference? Aim: What is the difference between precision and accuracy? Precision: how close are your measured values to each other Accuracy: how close are your measured values to the accepted value You just finished looking up the density of gold or silver in the quiz. D Au = 19.320 g/cm3 This is called the accepted value; it’s found in the reference table. Suppose two students measured the density of gold by experiment. Here are the values they obtained: Measured Values for Density of Gold STUDENT 1 STUDENT 2 19.300 g/cm3 18.561 g/cm3 19.310 18.560 19.330 18.562 19.315 18.562 1) Which student’s values are more accurate? Student 1 because they are closer to the accepted value. 2) Which student’s values are more precise? Student 2 because they are closer to each other. 3) Which is the most accurate measured value? 19.315 How accurate is it? % error = measured value – accepted value x 100 accepted value = 19.315 – 19.320 x 100 19.320 = - 0.005 x 100 19.320 = *0.03 % * Absolute value converts negative to positive