Undercoverage

Undercoverage occurs when an element of the target population is not represented on the survey frame and therefore not given any chance of selection in the survey sample; that is, the element has zero probability of selection into the sample. Undercoverage is the most serious type of coverage error because it can be difficult to detect and even more difficult to solve. Therefore, preventing undercoverage is often a priority during survey design. Large survey operations often plan and budget for extensive coverage evaluations. For example, a large sample survey called the Accuracy and Coverage Evaluation was conducted by the U.S. Census Bureau during Census 2000, with separate staff and separate physical office space. Its primary purpose was to evaluate the coverage of the census.

In household ...