Question: Manufacturing and Product Development The porosity of a concrete block is a measure (as a percentage) of the amount of empty space in the block. In residential homes with concrete-block foundations, a larger porosity leads to damper, colder basements. A contractor recommends pretreatment of concrete blocks with a product designed to decrease the porosity. A random sample of concrete blocks was obtained, and the porosity of each was measured. The clear, paintlike product was applied to each block, and the porosity was measured again. The differences (before treatment - after treatment) in porosities were recorded. Assume normality. Is there any evidence to suggest the new product decreases the mean porosity of concrete blocks? Use a = 0.001.