2.6 Determination of Size Parameters
Even though particle size distribution can be described by various models as outlined in the previous section, there were attempts to represent the PSD in more simplified ways. There is various size parameters used by several researchers and have been listed in Table 3 along with formula for their determination. The spread in particle size distribution from small to large is characterised by uniformity index. Mass relative span provides a dimensionless measure of particle size distribution. Folk and Ward (1957) have defined certain statistical parameters to define the particle size distribution which have been later used by other researchers (Folk,
1974; Bitra et al., 2008; Bitra et al, 2009). Skewness measures degree of asymmetry of normal distribution curve and its sign denotes whether a curve has an asymmetrical tail to
its left or right when distribution is plotted versus particle size. Kurtosis measures the sorting in the tails of distribution curve and the sorting in central portion. The kurtosis of particle size distribution includes 90% of the size distribution curve.