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GCSE Statistics · key term
A measure of how spread out data values are around their mean, expressed in the same units as the data.
Used by Edexcel
Specification 2a.09, 2b.02, 2c.01, 2c.02, 2c.04, 2c.05, 2c.06, 3p.12, 3p.13 · Paper 1, Paper 2
Revise: Determining skewnessDividing by the standard deviation takes account of the spread of the data. Both quantities have the same units, so the calculated skew has no units.
A measure of the spread of numerical data around its mean. A smaller standard deviation indicates that values are more closely clustered around the mean.
For standard deviation, divide by n or total frequency, not n − 1. Keep unrounded values during the calculation.
In a frequency table, fx² means f × x², not (fx)². For grouped intervals, use class midpoints and describe the resulting standard deviation as an estimate.
For these comparisons, pair the median with IQR, interpercentile range or interdecile range; pair the mean with standard deviation. Do not pair mean with IQR or median with standard deviation.
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A measure of spread about the mean, calculated by taking the square root of the mean of the squared deviations from the mean.
A measure of how spread out data values are around their mean; denotes the population standard deviation.
A measure of spread around the mean which uses all the data values and is expressed in the same units as the data.
A measure of how spread out data values are about their mean, expressed in the same units as the data.
A measure of how spread out data values are relative to their mean. It has the same units as the original data.
A measure of spread, written . A larger standard deviation means values are more spread out around the mean.
A measure of how spread out values are around their mean, measured in the same units as the data. Its symbol is .