Measurements & their errors Flashcards
accepted value
value of the most accurate measurement available, sometime referred to as the ‘true value’
accuracy
The closeness of a measurement to the true value (if known)
Base units
The units that define the SI system (e.g. the metre, the kilogram, the second, the ampere).
dependent variable
a physical quantity whose value depends on the value of another physical variable
differentiation
mathematical process of finding the gradient of a line from its equation.
error bar
representation of an uncertainty on a graph
independent variable
physical quantities whose values are selected or controlled by the experimenter
Integration
Mathematical process of finding the area under the curve from its mathematical equation
Limit of proportionality
The limits beyond which when a wire or a spring is stretched its extension is no longer proportional to the force that stretches it
linear
two quantities are said to have a linear relationship if the change of one quantity is proportional to the change of the other
linearity
an instrument that gives readings that are directly proportional to the magnitude of the quantity being measured
logarithmic scale
a scale such that equal intervals correspond to a change by a constant factor
mean value of a set of readings
sum of the readings divided by the number of readings
percentage uncertainty
=uncertainty/mean value x 100%
precision of a measurement
the degree of exactness of a measurement, usually expressed as the uncertainty of the readings used to obtain the measurement
precision of an instrument
the smallest non-zero reading that can be measured using the instrument, also sometimes referred to as the instrument sensitivity or resolution
random errors
errors vary randomly with no recognisable pattern or trend or bias
range of a set of readings
the difference between the largest and smallest reading
range of an instrument
the difference between the minimum and maximum reading that can be obtained using the instrument
reliability
an experiment or measurement is reliable if a consistent value is obtained each time it is repeated under identical conditions. The reliability of an experiment is increased if random and systematic errors have been considered and eliminated and, where appropriate, a more precise best fit line has been obtained.
repeatable
an experiment or measurement that gives the same results when it is repeated by the original experimenter using the same method and equipment
reproducable
an experiment or measurement that gives the same results when it is repeated by another person or by using different equipment or techniques.
sensitivity of an instrument
output response per unit input quantity
SI system
scientific system of units
systematic errors
differ systematically and show a pattern or trend or bias
uncertainty of a measurement
half the range of the readings used to obtain the measurement
valid measurement
measurements that give the required information by an acceptable method
zero error of an instrument
a systematic error due to a non-zero reading when the quantity to be measured is zero
