Glossary 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 quality values, which must be applied. For example, placing a thermometer in melting ice to see whether it reads zero in order to check that it is calibrated correctly.
Data
Information, either qualitative or quantitive, that has been collected.
Error
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, e.g the needle on an ammeter failing to return to zero when no current flows. A zero error May result in systematic uncertainty.
Evidence
Data which has 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, e.g a set of 11 readings equally spaced over a distance of 1 metre would give an interval of 10 centimetres.
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.
Prediction
A statement suggesting what will happen in the future, based on observation, experience or a hypothesis.
Range
The maximum and minimum values of the independent or dependent variables; important in ensuring that any pattern is detected. For example, a range of distances may be quoted as either: From 10cm to 50cm or from 50cm to 10cm.
Repeatable
A measurement is repeatable if the original experimenter repeats the investigation using the same method and investigation and obtains the same results.
Reproducible
A measurement is reproducible if the experiment is done by another person, or by using different equipment or techniques and the same results are obtained.
Resolution
Smallest change in the quantity being measured of a measuring instrument that gives a perceptible change in the reading.
Sketch graph
A line graph, not necessarily on a grid, that shows the general shape of the relationship between two variables. It will not have any points plotted and although the axes should be labelled they may not be scaled.
True value
This is the value that would be obtained in an ideal measurement.
Uncertainty
The interval within which the true value can be expected to lie. Whenever a measurement is made, there will always be some uncertainty or doubt about the result obtained. Uncertainty can be expressed in terms of spread of values obtained.
Validity
Suitability of the investigative procedure to answer the question being asked. For example, an investigation to find out if the rate of a chemical reaction depended upon the concentration of one of the reactants would not be a valid procedure if the temperature of the reactants was not controlled.
Valid conclusion
A conclusion supported by valid data, obtained from an appropriate experimental design and based on sound reasoning.
Variables
Physical, chemical or biological quantities or characteristics
Categoric
Values that are labels e.g names of plants
Continuous
Can have values that can be given a magnitude either by counting or by measurement
Control
One which may, in addition to the independent variable, affect the outcome of the investigation and therefore has to be kept constant or monitored
Dependent
Value measured for each and every change of the independent variable
Independent
Variable for which values are changed or selected by the investigator.
