How did analysts use data collected from Chicago teachers to determine who was cheating on standardized testing? What clues are found in the actual test answers to suggest it?

According to the Harper Collins, Student Guide, the case considers a group of ordinary people,school teachers,performing an ordinary task, testing their students.Recently,standardized testing has become mandatory in public schools.The No Child Left Behind law awards schools that make progress on these standardized tests and punishes schools that chronically lag behind.Levitt and a coauthor developed a computer algorithm to look for strings of suspicious answers on standardized tests.An analysis of data on the test scores of children in public schools in the Chicago Public School system reveals evidence that teachers cheat by substituting the right answers on students tests in about five percent of classes taught.