Semi Interquartile Range

Half the distance between the 25th to 75th percentile

Interpretation: the typical distance between an observed value and the sample median.

Distance between 25th and 75th is the interquartile range. The interquartile range tells us how spread out the middle part of the data is. In a box plot, this is the size of the box.

Half of that distance is the semi-interquartile range.

The semi-interquartile range is the typical difference of a score from the median. This tells about variability/dispersion, but not value. It tells the level of homogeneity or heterogeneity.

Other measures of variability or dispersion.