Table 3 Range, interquartile range and standard deviation of haemoglobin measurements from 48 intensive care patients listed in Table 1

Range

The values in this dataset range from 5.4 to 14.1 g/dl

Interquartile range

The median calculated in Table 2 splits the data into two equally sized groups. The lower and upper quartiles split the data into four equally sized groups (4 × 12) and are therefore most easily defined as the average of the 12th and 13th observations for the lower quartile and of the 36th and 37th observations for the upper quartile. In other words, the lower and upper quartiles are 8.7 and 10.8 g/dl, respectively. (There are more complicated methods for calculating the interquartile range [1], but these will not generally give markedly different results.)

Standard deviation (SD)

Using the formula given above: