Practical Terms Flashcards
define accuracy
a measure of the closeness of an individual test result and the true value
define precision
the closeness of agreement between measured values obtained by repeated measurements
define resolution
the smallest change in the quantity being measured that can be detected by an instrument
define an anomaly
a value in a set of results that does not fit the trend and is different to other repeats
define repeatability
the precision obtained when results are produced over a short timescale by one person using the same equipment in the same place
define reproducibility
the precision obtained when results are produced over a wider timescale by different people using equivalent equipment in different places
define uncertainty
- any measuring apparatus has uncertainty
- often taken to be half a division on either side of the smallest unit of the scale you are using
e.g if pipette has marks every 0.1 cm cubed, uncertainty is 0.05cm cubed
define random errors
due to judgement errors made by the experimenter
can be reduced by repeating the procedure several times
how do you calculate percentage uncertainty
uncertainty/quantity measured x100
define systematic errors
errors may be inherent in the equipment and repeated with every replicate
if the percentage error is known, a calculation can be done to determine the margin of error
define validity
a measurement is valid if it measures what it is supposed to be measuring
how can you increase the validity of an experiment
- controlling more variables
- improving measurement technique
- increasing randomisation to reduce sample bias
- adding a control
how to calculate percentage change
difference/original x100
