2.2.1: measurements and uncertainties Flashcards
define ‘error’
the difference between the result obtained, and the true value of the quantity
define ‘true value’
the value that would be obtained in an ideal measurement
define ‘measuring error’
the difference between the measured value and the true value
what causes errors
measuring devices or the design of the equipment
define ‘random error’
a measurement error in which the measurements vary unpredictably
what causes random errors
external factors affecting the environment or difficulty reading the measuring device
how can we correct random errors
we cannot correct random errors, however we can repeat the experiment and calculate the mean value
define ‘systematic errors’
a measurement error in which the measurement differs from the true value by a consistent amount each time
what causes systematic errors
the way a measurement is taken or a faulty measuring device
define ‘accuracy’
how close the measurement is to the true value (the closer the value, the more accurate it is)
define ‘precision’
how close repeated measurements are to each other (the closer they are, the more precise they are)
define ‘uncertainty’
the interval in which the true value of a measurement should lie
what is the equation for percentage uncertainty
(absolute uncertainty/actual value)x100
what are the rules for calculating overall uncertainties
when quantities have been added or subtracted, add the absolute uncertainties for each value
when quantities have been multiplied or divided, add the percentage uncertainty for each value
when a quantity is raised to a power ‘n’, multiply the percentage uncertainty by ‘n’
