Computer has a great potential to play a crucial role in testing. The enthusiasm in developing computer-based testing (CBT) in educational contexts has increased in recent years. Although computerized testing may be enticing, most testing practitioners find it necessary to offer their testing programs both in computerized and paper formats at the same time. If two versions of the same test are being offered simultaneously, or the paper-based version was delivered prior to the computer-based one, a comparability study for the equivalence of two sets of scores obtained from two different versions is required. The comparability study for the purpose of examining equivalence score is done to show the continuity of test and score reliability as well as the use of reliability and validity information developed from the paper version of the test. The standards for developing computerized test also need equivalent test scores to be established. Then, the effect of testing mode administration and the relationship of some learners' characteristics as external moderator factors such as prior computer familiarity, attitude and anxiety with testing performance are investigated in this book.