The accompanying data was obtained in a study to evaluate the liquefaction potential at...

The accompanying data was obtained in a study to evaluate the liquefaction potential at a proposed nuclear power station (“Cyclic Strengths Compared for Two Sampling Techniques,” J. of the Geotechnical Division, Am. Soc. Civil Engrs. Proceedings, 1981: 563–576). Before cyclic strength testing, soil samples were gathered using both a pitcher tube method and ablock method, resulting in the following observed values of dry density (lb/ft³):

Calculate and interpret a 95% CI for the difference between true average dry densities for the two sampling methods.