Item analysis is one of the most important elements of test construction. Statistical techniques can be used to carefully examine how a test item functions. This analysis can reveal how easy or difficult an item is and how well the item discriminates between test-takers. Item analysis can also reveal whether an item functions similarly when administered to different populations or when it is translated into another language. Classical test theory (CTT) and item-response theory (IRT) are the two commonly used methods of assessing test item characteristics.