Measurements and Errors Flashcards
Random Error
Cause differences in measurements spread about the mean
Reduce Random Errors
- take at least 3 repeats and then calculate the mean
- can eliminate anomalies
- use computer/ data loggers to reduce human error and enable smaller intervals
- use appropriate equipement with appropriate resolution
Systematic Error
Where all results are either too high or too low by the same amount
Reduce Systematic Errors
- calibrate apparatus by measuring a known value
- in radiation, measure background radiation and subtract from final result
- read the meniscus at eye level and use controls in experiments
Precision
Precise measurements are consistent (fluctuate slightly about a mean)
Repeatability
If the original experimenter can redo the experiment with the same equipment and method to get the same results, it is repeatable
Reproducibility
If the experiment is redone by a different person or with different techniques and equipment to get the same results, it is reproduciable
Resolution
Smallest change in quantity being measured that gives a recognisable change in reading
Accuracy
A measurement close to the true value is accurate
Absolute Uncertainty
Uncertainty as a fixed quantity 273 +- 2K
Percentage Uncertainty
Uncertainty as a percentage of the measurement 9 +- 2% K
Reading
When 1 value is found (eg: thermometer)
Measurement
Where 2 values are found (eg: ruler has starting point and end point)
Uncertainty in a Reading
+- half smallest division
Uncertainty in a Measurement
+- smallest division
