1. 1.2 Measurements in Experiments
Chapter 1 Section 2
Part 2 – Accuracy, Precision & Significant Figures

2. Accuracy
Accuracy – The extent to which a reported measurement approaches the true value of the quantity measured.
Closer to the middle of the bulls eye, the more accurate the measurement.

3. Precision
Precision – The degree of exactness or refinement of a measurement.
How close are the measurements together.

4. Not Accurate or Precise
Accurate and Precise
It is possible for objects to be both accurate and precise of none.
Accurate and Precise
Not Accurate or Precise

5. Significant Figures
Significant Figures – Those digits in a measurement that are know with certainty plus the first digit that is uncertain.
The measurement can not be more precise then the measuring device.
Example: I can not measure inches using the odometer in a car, even though an odometer measures length.

6. Rules of Zeros for Sig Figs
Zeros between other nonzero digits are significant.
Example: 50.3 seconds (3 sig figs)
Zeros in front of nonzero digits are not significant.
Example: (2 sig figs)
Zeros that are at the end of a number and also to the right of the decimal are significant.
Example: (5 sig figs)

7. Rules (cont.)
4. Zeros at the end of a number but to the left of a decimal are significant if they have been measured or are the first estimated digit; otherwise, they are not significant.
Example: 1000 m (1 sig figs)
1000. m (4 sig figs)

8. Addition and Subtraction Rule
The final answer should have the same number of digits to the right of the decimal as the measurement with the smallest number of digits to the right of the decimal.
97.3
→ round off → 103.2

9. Multiplication and Division Rule
The final answer has the same number of significant figures as the measurement having the smallest number of significant figures.
123 x
→ round off → 658

10. Practice Problems
List how many significant figures are in each number.
23.56 m
sec hz
1000 kg g
10.40 m/s