The 3-parameter model of Item Response Theory gives the probability of an individual (examinee) responding correctly to an item without being sure of all the facts. That is known as guessing. Guessing could be a strategy employed by examinees to earn more marks. The way an item is constructed could expose the item to guessing by the examinee. A study on comparison of the Psychometric properties of the Biology Examinations conducted by West African Examination Council and National Examination Council, in the year 2000, identified items that were prone to guessing.