Statistics in soil science

Key points
• Soil varies from place to place; statistics is a technology for describing that variation quantitatively and separating signal
from noise.
• Replicate sampling is required to estimate the variation in experimental material and geographic regions.
• Randomization is needed to estimate mean values and their variances, and to place confidence limits on means.
• Data can be summarized by means, medians, variances, standard deviations and skewness coefficients.
• Distributions of data are best illustrated by histograms and Q–Q plots.
• Analysis of variance apportions the variance in a set of data to sources in the designs of experiments and surveys; any actual
analysis must fit the design by which the data have been obtained.
• Relations among two or more measured variables are expressed by Pearson correlation coefficients.
• A variable may be predicted from one or more others on which it depends by regression.