Uncertainty in Measurement
In chemistry, we must take measurements from some devices/apparati
(graduated cylinders, burettes, etc.).
When taking these measurements there are certain digits and uncertain
digits.
An uncertain digit is the rightmost digit in a recorded number. Usually only
one recorded.
A measurement always has some degree of uncertainty!
The collection of certain and 1 uncertain digits recorded or used for a
measurement are collectively called the significant figures.
Uncertainty is implied in the rightmost digit to be +/- 1 unless otherwise
noted.
Precision and Accuracy
Although in everyday practice these two words are used interchangeably,
they do mean two different things:
Accuracy – refers to the agreement of a given value to the true value
Precision – refers to the degree of agreement among several measurements
of the same quantity. (Reproducibility of a repeated measurement)
(See dart board example)
