Various varying variances: The challenge of nuisance parameters to the practising biostatistician

Stephen Senn1

  • 1CRP Santé, Luxembourg, UK Stephen.Senn@crp-sante.lu.

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The range is a simple measure of variability, indicating the difference between the highest and...
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The deviations show how spread out the data are about the mean. A positive deviation occurs when the data value exceeds the mean, whereas a negative deviation occurs when the data value is less than the mean. If the deviations are added, the sum is always zero. So one cannot simply add the deviations to get the data spread. By squaring the deviations, the numbers are made positive; thus, their sum will also be positive.The standard deviation measures the spread in the same units as the data.
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