A computer-assisted technique is the most helpful method for an IS auditor to determine whether duplicate vendor payments exist on a complex system with a high volume of transactions. A computer-assisted technique is a tool or procedure that can be used to perform audit tests or procedures on data stored in electronic form. Examples of computer-assisted techniques include data analysis software, query tools, scripting languages, and specialized audit software. A computer-assisted techniquecan help an IS auditor to identify and extract duplicate payments from a large data set, perform calculations and comparisons, and generate reports and summaries. A computer-assisted technique can also provide more accuracy, efficiency, and coverage than manual methods.
Stratified sampling, statistical sampling, and process walk-through are not as helpful as a computer-assisted technique for this purpose. Stratified sampling is a sampling method that divides the population into subgroups based on certain characteristics and selects samples from each subgroup. Statistical sampling is a sampling method that uses probability theory to determine the sample size and selection criteria. Process walk- through is a review technique that involves following a transaction or process from start to finish and observing the inputs, outputs, controls, and documentation. These methods may be useful for other audit objectives, but they are not as effective as a computer-assisted technique for detecting duplicate payments in a complex and high-volume system. References: ISACA Frameworks: Blueprints for Success, [ISACA Glossary of Terms]

File checksums are values that are calculated from the contents of a file and can detect any changes or corruption in the file. They are used to verify that the files that are transferred or processed through system interfaces are not altered in any way. File checksums are more effective than periodic audits, file counts, or IT operator monitoring, which are other types of controls that can help ensure the integrity of system interfaces, but they are not as reliable or timely as file checksums.

The most important thing for the organization to ensure when reducing the actual retention period for media containing completed low-value transactions is that the retention period complies with data owner responsibilities. Data owners are accountable for the quality, security, and availability of the data under their control. They are also responsible for defining and enforcing data retention policies that comply with legal, regulatory, contractual, and business requirements. Data owners should be consulted and involved in any decision that affects the retention period of their data, as they are ultimately liable for any consequences of data loss or breach.
The policy includes a strong risk-based approach, the retention period allows for review during the year-end audit, and the total transaction amount has no impact on financial reporting are not the most important things for the organization to ensure when reducing the actual retention period for media containing completed low- value transactions. These are possible factors or benefits that may influence or justify the decision, but they do not override or replace the data owner responsibilities.

ISACA defines sufficient and appropriate evidence as the standard for audit conclusions. Appropriateness relates to relevance (applicability) and reliability (persuasiveness). Evidence that is persuasive and directly applicable to the audit objective provides stronger assurance than evidence that is merely timely, complete, or reasonable. While the other options describe desirable qualities, they do not encompass the full ISACA standard. Thus, the most complete characterization of quality evidence is that it must be persuasive and applicable to the audit's purpose.
References (ISACA): ISACA Audit and Assurance Standards; ISACA ITAF Guidelines on Evidence.

Comprehensive and Detailed Explanation:
A Certification Practice Statement (CPS) is a detailed document that describes the practices a Certificate Authority (CA) uses when issuing and managing digital certificates. It includes procedures for handling compromised private keys, revocation, renewal, and security controls.
* Certificate policy (B): High-level rules governing certificate usage, but not operational details.
* PKI disclosure statement (C): Provides users with general PKI-related information.
* Certificate revocation list (D): A technical mechanism listing revoked certificates, but not the procedures for managing compromise.
# ISACA Reference: CISA Review Manual 27th Edition, Domain 5, section on PKI components and certificate lifecycle management.