I am asking this question in context to section 4.1 in this paper: 
security control methods for statistical Database
(<http://www.utdallas.edu/~muratk/courses/privacy08f_files/stat_database_sec.pdf>)

As I am not statistician or Mathematician so I had hard time understanding it. If someone could explain what is statistical bias or the bias problem in section 4.1 of this paper, that would be great :).

Thanks! :)