1. Measurement

2. Measurements science is based on measurements all measurements have: – magnitude – uncertainty – units Numbers mathematics is based on numbers exact numbers are obtained by : – counting – definition

3. Measurements Measurements are not numbers – Numbers are obtained by counting or by definition; measurements are obtained by comparing an object with a standard “unit” – When you say that a table is 2 meters long, you are really saying that the table is two times longer than an object that is 1 meter long

4. Measurements Numbers are exact; measurements are inexact Mathematics is based on numbers; science is based on measurement

5. Uncertainty in Measurement Comparison with a unit or a scale of units always involves some uncertainty Estimate between the smallest scale divisions The digit between the lines is always uncertain (estimated)

6. Uncertainty in Measuring Devices There is a limit to the precision of a measurement The scientist making the measurement must decide the uncertainty value for a particular measuring device. See “Scale Reading, Uncertainty and Significant Figures”

7. Significant figures Significant figures are the digits in a measurement known with certainty plus one digit that is uncertain (estimated)