Dispersion Measure

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A Dispersion Measure is a measure of how stretched or squeezed a probability distribution is.



References

2016

Range
The range of a set of measures is simply the difference between the largest and the smallest measurement value.
Thus, for example, if you have a set of measures (21, 22, 26, 19, 12, 24, 33) then you first find the highest measure (33) and subtract the lowest measure (12) to give the range (21). This is easy to calculate, but there can be several problems with using it:
  • Special causes of variation can cause an unrealistically wide range.
  • As more measurements are made, it will tend to increase.
  • It gives no indication of the data between its values.
Standard deviation
The standard deviation is a number which is calculated using a simple mathematical trick (calculating the square root of the average of squares) to find an 'average' number for the distance of the majority of measures from the mean.
The standard deviation is of particular value when used with the Normal distribution, where known proportions of the measurements fall within one, two and three standard deviations of the mean (...)=== 2013 ===