Subject Specific Vocabulary (Science)

Accuracy
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Terms in this set (30)
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 TestA fair test is one in which only the independent variable has been allowed to affect the dependent variable.Hypothesisa proposal intended to explain certain facts or observationsIntervalThe quantity between readings, eg a set of 11 readings equally spaced over a distance of 1 metre would give an interval of 10 centimetres.PrecisionPrecise 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.RangeThe maximum and minimum values of the independent or dependant 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'.RepeatableA measurement is repeatable if the original experimenter repeats the investigation using same method and equipment and obtains the same results.ReproducibleA measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained.ResolutionThis is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading.Sketch GraphsA 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 ValueThis is the true value that would be obtained in an ideal measurement.PredictionA prediction is a statement suggesting what will happen in the future, based on observation, experience or a hypothesis.uncertaintyThe interval within which the true value can be expected to lie, with a given level of confidence or probability.ValiditySuitability of the investigation 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 ne of the reactants would not be a valid procedure if the temperature of the reactants was not controlled.Valid ConclusionA conclusion supported by valid data, obtained from an appropriate experimental design and based on sound reasoning.VariablesThese are physical, chemical or biological quantities or characteristics.CategoricCategoric variables have values that are labels, eg names of plants or types of material.ContinuousContinuous variables can have values (Called a quantity) that can be given a magnitude either by counting (as in the case of the number of shrimp) or by measurement (eg light intensity, flow rate etc.) previously known as discrete variable.ControlControl Variable in one which may, in addiction to the independent variable, affects the outcome of the investigation and therefore has to be kept constant or at least monitored.DependantDependant Variable is the variable of which the value is measured for each and every change in the independent variable.IndependentIndependent variable is the variable for which values are changed or selected by the investigation.