Accuracy & Precision

-Precision: how reproducible a measurement is compared to other measurement
-Accuracy: how close the measurement for average measurement comes to the accepted or real value

Measurement and Uncertainty
-no measurement is exact
-every measurement is a best estimate
-countable number is exact number

Absolute Uncertainty
-expressed in units of measurement, not as a ratio
Method1:
-make at least 3 measurement, calculate the average
-the absolute uncertainty is the largest difference between the average and the lowest and highest.

Ex:
1  15.3g                                                           average: 15.3g
2  15.5g                                                           AU: 15.3 ± 0.2g
3  15.2g
4  11.9g(remove)
5  15.3g

Method2:
determine the uncertainty of each instrument.
always measure to the best precision that you can.

Relative Uncertainty & Significant Figure

RU=AU/estimate uncertainty            Ex: 39.3±0.1g  RU = 0.1/39.3×100%

or using Sig Fig: the last number in the measurement is uncertain