Soil resistivity is used in studies of corrosion of pipes buried in the soil. For example, a resistivity of 0 to 400 ohms/cm represents extremely severe corrosion conditions; 400 to 900, very severe; 900 to 1500, severe; 1500 to 3500, moderate; 3500 to 8000, mild; and 8000 to 20,000, slight risk. There were 32 measurements of soil resistivity made at a prospective construction site.
Compute sample mean and variance. Construct a histogram using the classification bands above as intervals. Illustrate the same relations on the cumulative frequency distribution and indicate the observed relative frequency of occurrence. Note that the mean represents a spatial mean and that the variance is a measure of lack of homogeneity of the resistivity property over the site.