In a symmetric distribution, an interval stretching from one semi-quartile range below the median to one semi-quartile above the median will contain one-half of the values.

The semi interquartile range is half of the interquartile range.

The semi –interquartile range is one half of the interquartile range.

The semi-quartile range is another measure of spread.

Although standard deviation is less susceptible to extreme values than the range, standard deviation is still more sensitive than the semi-quartile range.