Glossary
KEY TERMS
accepted value
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The accepted value of a measurement is the value of the most accurate measurement available. It is sometimes referred to as the “true” value. Use scientific literature to find accepted/known values.
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accuracy
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Accuracy is a measure of how near the measurements are to the accepted/known values.
For further details, see https://www.matrix.edu.au/the-beginners-guide-to-physics-practical-skills/physics-practical-skills-part-2-validity-reliability-accuracy-experiments/ |
dependent variable
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Dependent variables are those variable physical quantities whose values change as a result of a change of value of another variable quantity. The dependent variable is usually plotted on the vertical or y-axis of a graph.
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average (mean) value
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The average (mean) value of a set of readings is calculated by adding the readings together and dividing by the number of readings.
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error
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The difference between a measurement and its accepted value. Often a misnomer suggesting that a mistake was made in taking a reading.
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extrapolation
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Using a graph to predict values that fall outside of the range of data points taken.
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independent variable
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Independent variables are those variable physical quantities whose values are controlled or selected by the experimenter. Changing the value of an independent variable usually results in a change of value of a dependent variable. The independent variable is usually plotted on the horizontal or x-axis of a graph.
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interpolation
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Using a graph to predict values that fall within the range of data points taken.
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precision (of a data set)
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A set of data is precise or has high precision it if repeated measurements show the same results under unchanged conditions (e.g. same equipment, same day). The greater the scatter/difference in repeated measurements, the lower the precision.
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precision (of a measurement)
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The precision of a single measurement relates to the number of significant figures, for example 2.14 is more precise than 2.14. It is related to the resolution of a measuring instrument.
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random error
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Random errors are errors affect each measurement differently. Readings with random errors vary in an unpredictable manner with no discernable pattern or trend. The effect of random variations in measurements of a quantity is reduced by taking more readings and finding an average value.
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range
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The range of a set of readings or calculated values is the difference between the smallest value and the largest value.
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reliable
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Reliability is about how reproducible results are in a different environment. Results are reliable when similar results are produced for an experiment repeated under consistent but changed conditions (e.g. different equipment, different day). Precision is related closely to reliability.
For further details, see https://www.matrix.edu.au/the-beginners-guide-to-physics-practical-skills/physics-practical-skills-part-2-validity-reliability-accuracy-experiments/ |
resolution
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The resolution of an instrument is the smallest reading that can be measured using the instrument.
Below, the ruler on the left has a resolution of 1 cm since the smallest markings on the ruler are the 1 cm lines. The ruler on the right has a resolution of 1 mm. The ruler on the right has a higher resolution than the one on the left. |
sample size
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Sample size refers to the number of times a measurement will be taken. Most experiments conduct a number of trials (take a measurement a number of times) and the results are then averaged to reduce the effect of random error.
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systematic error
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Systematic errors cause a consistent change in the measured values (change every measurement in the same way). They can result from an instrument calibration error, from the incorrect use or reading of instruments or poor experimental design.
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valid
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Valid data is evidence that is reliable and relevant to the question being investigated. An experiment is valid if it is:
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zero error
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This error is when an instrument gives a non-zero reading when it should read zero. It is a systematic error which must be added to (or subtracted from) all readings obtained with a particular instrument. A common example is an electronic scale that gives a non-zero reading when there is nothing on it.
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