Measurements and their errors Flashcards
What is a random error?
Affects precision, causes measurements to spread about the mean
True or false, you cannot get rid of all random errors
True
How do you reduce random error?
Take repeats and calculate a mean (this also allows anomalies to be identified)
Use computers/ data loggers/ cameras too reduce human error and enable smaller intervals
Use appropriate equipment, for example a micrometre vs a ruler due to its resolution
What is a systematic error?
Affects accuracy, due to apparatus or faults in method. The result is either too high or too low by the same amount every time.
How do you reduce systematic error?
Calibrate your apparatus with a known value or Zero
Use controls in experiments
Read values at eye level too avoid parallax
Account form background radiation in radiation experiments
Define precision
Precise measurements are consistent, they fluctuate slightly about a mean
value - this doesn’t indicate the value is accurate
Define repeatability
If the original experimenter can redo the experiment with the same
equipment and method then get the same results it is repeatable
Define reproducibility
If the experiment is redone by a different person or with different techniques
and equipment and the same results are found, it is reproducible
Define resolution
The smallest change in the quantity being measured that gives a
recognisable change in reading
Define accuracy
A measurement close to the true value is accurate
What is the uncertainty of a group of repeating data?
(+- range/2 ) / mean
How do you combine uncertainties when: adding/ subtracting data?
Add the absolute uncertainties
How do you combine uncertainties when: Multiplying / Dividing data?
Add the percentage uncertainties
How do you combine uncertainties when: Raising to a power?
Multiply the percentage uncertainty by the power
