You Have Been Hired as a Consultant by Building Contractor

You have been hired as a consultant by building contractor, who have been sued by the owners' representatives of a large condominium project for shoddy construction work. In order to assess the damages for the various units, the owners' association sent out a letter to owners and asked if people were willing to make their units available for destructive testing. Destructive testing was conducted in some of these units as a result of the responses. Based on the tests, the owners' association inferred the damage over the entire condo complex. Do you think that the inference is valid in this case? Discuss how proper sampling should proceed in this situation.