In the Census, each household can identify itself as either a "family" household or a "non-family" household. Examples of a non-family household are single person households and groups of students who share a house. Alameda County has hundreds of thousands of households, of which 65% are family households. The rest are non-family households. San Francisco County also has hundreds of thousands of households of which 44% are family households. A simple random sample of 400 households is taken in Alameda County. Independently, a simple random sample of 400 households is taken in San Francisco County.