7. The method of claim 6 , wherein the incorrect input type comprises any one of an incorrect input due to a continuous key press, an incorrect input due to an adjacent key press, an incorrect input due to a key omission, and an incorrect input due to a key input order.
6. The method of claim 4 , wherein determining the each cost of the insert operation, delete operation, and replace operation corresponding to the identified keypad type comprises: identifying at least one or more incorrect input types having a high frequency of occurrence associated with the identified keypad type; if operating conditions of at least one or more incorrect input types having a high frequency of occurrence are met, determining the cost of the insert operation, the delete operation, or the replace operation as a first value and, otherwise, determining the cost of the insert operation, the delete operation, or the replace operation as a second value higher than the first value; and determining the cost of the insert operation, the delete operation, or the replace operation as a basic cost whether the operating conditions are met or not.