StatisticsMeasures of Dispersion

How much a set of data is scattered — its dispersion — is measured from the observations themselves, and from whichever measure of central tendency we choose to measure it about. Four measures of dispersion are in common use:

(i) Range, (ii) Quartile deviation, (iii) Mean deviation, (iv) Standard deviation.

This chapter covers all of them except the quartile deviation. Along the way you will also meet the variance, the square of the standard deviation.

Centre or spread? Drag each measure into the right bucket.

Every measure in the second bucket answers the coach's real question — how consistent is the data? Let us build them one at a time, starting with the simplest.