The cumulative frequency distribution (CDF) curves of the metal’s data sets were used to estimate baseline metal concentrations. Usually, a CDF curve is plotted with the data on abscissa and the corresponding estimated percentiles on ordinate. The reverse convention, as in the present study, can also be used if percentile/s following certain sample value is to be found.
The CDF curves were drawn by statistical software Minitab 161. The normality of the distribution of metals’ data was investigated by performing one-sample Kolmogorov–Smirnov test (or the K–S test of normality). It was found that datasets of metals were either normally (for Cr and Fe) or log-normally distributed (for Cu, Zn and Pb). The data of Cu, Zn and Pb was therefore log-transformed prior to the CDF plotting. Then, CDF curves for Fe and Cr were drawn by
The cumulative frequency distribution (CDF) curves of the metal’s data sets were used to estimate baseline metal concentrations. Usually, a CDF curve is plotted with the data on abscissa and the corresponding estimated percentiles on ordinate. The reverse convention, as in the present study, can also be used if percentile/s following certain sample value is to be found. The CDF curves were drawn by statistical software Minitab 161. The normality of the distribution of metals’ data was investigated by performing one-sample Kolmogorov–Smirnov test (or the K–S test of normality). It was found that datasets of metals were either normally (for Cr and Fe) or log-normally distributed (for Cu, Zn and Pb). The data of Cu, Zn and Pb was therefore log-transformed prior to the CDF plotting. Then, CDF curves for Fe and Cr were drawn by
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