For each of 18 preserved cores from oil-wet carbonate reservoirs, the amount of residual gas saturation after a solvent injection was measured at water flood-out. Observations, in percentage of pore volume, were 23.5 31.5 34.0 46.7 45.6 32.5 41.4 37.2 42.5 46.9 51.5 36.4 44.5 35.7 33.5 39.3 22.0 51.2

(See “Relative Permeability Studies of Gas-Water Flow Following Solvent Injection in Carbonate Rocks,” Soc. Petroleum Engineers J., 1976: 23–30.)

a. Construct a boxplot of this data, and comment on any interesting features.

b. Is it plausible that the sample was selected from a normal population distribution?

c. Calculate a 98% CI for the true average amount of residual gas saturation.