Errors in Measurement-Accuracy and Precison
- 1. Physics Sept 6th, 2023 Topic: Errors and accuracy Whatever you do, do it well
- 2. Errors
- 3. What is an error? A measure of the estimated difference between the observed or calculated value of a quantity and its true value. There are two types of errors that are commonly associated with measuring, (namely), 1. random 2. systematic errors.
- 4. Random errorr? Random Errors are errors that are due to the experimenter and can usually be improved upon. For example: a. Reaction time when using the stopwatch b. Parallax error c. Errors due to environment
- 5. Parallax error Parallax errors occur when we do not position our eyes directly above the measurement we are reading as so the reading is slightly off.
- 6. Systematic Errors Systematic errors are errors due to the equipment which we are unable to fix or minimise. They will be in every reading we measure with the instrument. For example, If the stopwatch is 2 seconds fast or the triple beam balance does not zero properly. Or when we press the button on the stopwatch, there is a very, very small time delay for the stopwatch to respond.
- 8. Accuracy and precision Accuracy is the closeness of agreement between a measured value and a true or accepted value. Measurement error is the amount of inaccuracy. Precision is a measure of how well a result can be determined (without reference to a theoretical or true value). It is the degree of consistency and agreement among independent measurements of the same quantity; also the reliability or reproducibility of the result. Accuracy depends on the experimenter while precision depends on the instrument. You cannot be more precise than your instrument. Nb Accuracy is how close a value is to the true value While Precision is the exactness of the value I.e as the unit gets smaller the value gets more precise.
- 9. precision of an instrument The metre ruler has a precision of 1mm = 0.1cm The tbb has a precision of 0.1g The stopwatch has a precision of 0.01s
- 10. precision of an instrument The error associated with any value read from the instrument is 1⁄2 of the precision. However the error in a measured value is the precision. Explain.
- 14. Comment on the accuracy and precision of these results