scope:

This standard guideline outlines a procedure to optimize the fitting and goodness-of-fit testing of a probability density function (pdf) to a sample of saturated hydraulic conductivity (K) measurements. The procedure assumes a uniform scale of observation (similar measuring device) and statistically homogeneous and independent hydraulic conductivity measurements. Two pdfs are recommended for fitting purposes when such a sample of saturated hydraulic conductivity measurements is available. The first is the lognormal pdf, recommended when logarithmically transformed K data have coefficient of skew (C_sY) in the range-0.05 ≤ C_sY ≤ 0.05. The second is the (three-parameter) log-gamma pdf, recommended when logarithmically transformed K data have coefficient of skew |C_sY| > 0.05. Testing the goodness-of-fit to K data achieved by the lognormal or the log-gamma pdfs is performed with the chi-squared method.