2. Is the data complete enough?

In an ideal world you would have a perfect and complete set of data within a database so that it can answer all the questions for which it was built.

But quite often it is not possible or practical to have a complete set of data.

Example: The Census

Every ten years, the UK government sends out a census form to all households. The details of every person in the household must be recorded and the form returned to the government. If they do not do this they face getting charged a large fine.

A vast amount of information is collected which helps the government to plan for the future. For example whether we need more roads, more housing, more schools etc.

However, even though a lot of data is collected it is not complete or necessarily accurate. What about homeless people? They never received a form. What about those households that don't complete their forms? What about people who tell lies on their forms?