Keywords Flashcards
Accuracy
A measurement result is considered accurate if it is judged to be close to the true value
Calibration
Marking a scale on a measuring instrument. This involves establishing the relationship
between indications of a measuring instrument and standard or reference quantity values,
which must be applied. For example, placing a thermometer in melting ice to see whether it
reads zero, in order to check if it has been calibrated correctly.
Data
Information, either qualitative or quantitative, that has been collected
Error
See also uncertainty
Measurement error
The difference between a measured value and the true value
Anomalies
These are values in a set of results which are judged not to be part of the variation caused by random uncertainty
Random error
These cause readings to be spread about the true value, due to results varying in an
unpredictable way from one measurement to the next. Random errors are present when any
measurement is made, and cannot be corrected. The effect of random errors can be reduced
by making more measurements and calculating a new mean.
Systematic error
These cause readings to differ from the true value by a consistent amount each time a
measurement is made. Sources of systematic error can include the environment, methods of
observation or instruments used. Systematic errors cannot be dealt with by simple repeats. If
a systematic error is suspected, the data collection should be repeated using a different
technique or a different set of equipment, and the results compared.
Zero error
Any indication that a measuring system gives a false reading when the true value of a
measured quantity is zero, eg the needle on an ammeter failing to return to zero when no
current flows. A zero error may result in a systematic uncertainty.
Evidence
Data which has been shown to be valid
Fair test
A fair test is one in which only the independent variable has been allowed to affect the dependent variable
Hypothesis
A proposal intended to explain certain facts or observations
Interval
The quantity between readings, eg a set of 11 readings equally spaces over a distance of 1m would give an interval of 10 cm
Precision
Precise measurements are ones in which there is very little spread about the mean value.
Precision depends only on the extent of random errors - it gives no indication of how close results are to the true value.
Prediction
A prediction is a statement suggesting what will happen in the future, based on observation, experience or a hypothesis.