Modeling internal controls of automated teller machine (ATM) systems: A computerized decision aid for design and evaluation

The study identifies and models internal controls of automated teller machine systems used by the banking industry. A reliability model of internal controls of ATM systems using series, parallel, and simple structures is presented. Control items and relationships are justified based on the engineering, computer, and auditing literatures. Use and limitations of this model are also discussed. An ATM case with fixed controls and a related questionnaire has been developed. A computerized decision aid programmed in the PC BASIC language for assisting design and evaluation of the ATM internal control system has been developed and evaluated. To evaluate the modeling effectiveness, a small group of graduate students in the EDP Auditing master program uses the decision aid to evaluate the ATM base by filling out the questionnaire. Computed values are compared with the user-assigned values to examine differences between model results and human judgements