Oct. 28, 2010 Relative + Absolute Uncertainty

PRECISION is how many times a certain measurement figure appears compared to other measurements taken. (e.g. how many times 2.3 is the result)

ACCURACY is how close your measurement is to the real or accepted number or figure. ( 2.3 ---real value is 2.4)

ABSOLUTE UNCERTAINTY:

-measured in the units, not expressed as a ratio

-2 methods of calculation
-1. Find the average of your measurements(take at least 3). The greatest difference between the measurement amounts is the absolute uncertainty.
****Discard the value that is either much larger or smaller than others.

Ex. Values: 12.2, 12.4, 12.4, 12.2, 11.7

1. Discard 11.7.
2. Find the average (12.2+ 12.4 + 12.4 +12.2/4 = 12.3
3. Find largest difference ( 12.4-12.2 = 0.2)
4. Absolute uncertainty is 12.3 +-0.2

-2. The uncertainty of instruments of measurement
Find the smallest unit/segment of measurement and estimate to fraction of 0.1.
(e.g. 1 mL = 0.1 mL)

RELATIVE UNCERTAINTY

absolute uncertainty / estimated measurement

Absolute uncertainty can be expressed as %

The number of significant figures reveals the relative uncertainty