1. What is a reading? It is the single determination of the value of an unknown quantity It is the actual reading taken in an experiment

2. Measurements This is the final result of the analysis of a series of readings It is accurate up to a certain degree depending on the instruments used and the constrains of the observer Any quantity being measured has an amount of uncertainty or error associated with it

3. Example 34.7cm The error associated with this reading is 0.1cm It is represented as 0.1 cm represents the absolute error

4. Fractional error Absolute error/reading

5. Percentage error (Absolute error/ reading) * 100%

6. Types of errors Systematic Random

7. Systematic Due to instruments Faults in the surrounding conditions Mistakes made by the observer The size of the error is roughly constant and it is always greater or less than the actual value

8. Sources of Systematic Errors Zero errors example in stop watches, micrometer screw guage Personal error example reaction time of the observer Errors due to the instrument Errors due to wrong assumption

9. IMPORTANT Systematic errors cannot be reduced by taking a large number of readings using the same method, same instrument an the same observer. It can only be reduced by taking measurements carefully, using different instruments and different methods

10. Random errors Uncertainties in a measurement made by the observer or person who takes the measurement It can be positive or negative It’s magnitude is not constant

11. Examples of Random Errors Parallax Application of different pressures to close a micrometer screw gauge Changes in temp during an experiment

12. Precision Diameter (mm)Deviation 0.380.02 0.360.04 0.40 0.440.04 0.420.02 0.40.024 Diameter (mm)Deviation 0.40 0.410.01 0.390.01 0.420.02 0.380.02 0.40.012

13. Accuracy A measurement is said to be accurate if it is close to the actual value This is found by using the percentage error Consider the following: Which has a higher degree of accuracy?

14. Compound Errors