Permeability of sandstone during weathering. Natural stone, such as sandstone, is a popular building construction material. An experiment was carried out in order to better understand the decay properties of sandstone when exposed to the weather (Geographical Analysis, Vol. 42, 2010). Blocks of sandstone were cut into 300 equal-sized slices and the slices randomly divided into three groups of 100 slices each. Slices in group A were not exposed to any type of weathering; slices in group B were repeatedly sprayed with a 10% salt solution (to simulate wetting by driven rain) under temperate conditions; and slices in group C were soaked in a 10% salt solution and then dried (to simulate blocks of sandstone exposed during a wet winter and dried during a hot summer). All sandstone slices were then tested for permeability, measured in milliDarcies

(mD). These permeability values measure pressure decay as a function of time. The data for the study

(simulated) are saved in the SAND file. Measures of central tendency for the permeability measurements of each sandstone group are displayed in the MINITAB printout on p. 92.

a. Interpret the mean and median of the permeability measurements for group A sandstone slices.

b. Interpret the mean and median of the permeability measurements for group B sandstone slices.

c. Interpret the mean and median of the permeability measurements for group C sandstone slices.

d. Interpret the mode of the permeability measurements for group C sandstone slices.

e. The lower the permeability value, the slower the pressure decay in the sandstone over time. Which type of weathering (type B or type C) appears to result in faster decay?

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Descriptive Statistics: PermA, PermB, PermC N for Variable PermA N Mean Median Mode Mode 100 73.62 70.45 59.9, 60, 60.1, 60.4 2 PermB PermC 100 128.54 139.30 146.4, 146.6, 147.9, 148.3 100 83.07 78.65 3 70.9 3 The data contain at least five mode values. Only the smallest four are shown.