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
