For a multi-family housing inspection, what percentage of similar units built before 1960 (or unknown) do you test/sample?
You test at least 5.8% of them. You round up if it isn't a whole number.
Should every unit be given a sequence number? If so why?
Yes, so that random assignment can be conducted.
Testing combination should be listed on the report. What is the minimum number of testing combination of a given component type of be used and valid?
At least 40 testing combinations of a given component type must be used to be valid with the desired level of confidence
If the majority of a given tested combinations are positive then
the untested similar component types are assumed to be positive.