Certified Quality Auditor (CQA) Prasctice Exam

An auditor is performing an audit of a drilling machine that produces 100 pieces a day and that is showing improved quality. Which of the following rules should be used for determining the proper sample size for a fixed level of confidence?

1. The moving average should be calculated.

2. The sample size should be decreased as the quality improves.

3. The AQL of the raw material should be used.

4. A 10% sample size should be used, regardless of the change in quality.

The correct answer is: The sample size should be decreased as the quality improves.

The correct choice emphasizes the relationship between sample size and quality levels in an auditing context. As quality improves, it is logical to adjust the sample size accordingly. This is based on the principle that when a process is performing well and producing fewer defects, there is less variability present, which implies that fewer samples might be needed to accurately assess the quality. In practical terms, if the production process is demonstrating consistent quality improvements, it supports the idea that the items being produced are more likely to meet the quality standards. Therefore, reducing the sample size can still provide a reliable assessment of the overall quality without compromising the integrity of the audit. This approach is efficient and resource-conscious, allowing auditors to focus their efforts where they're most needed without unnecessary over-sampling. On the other hand, other options do not align with this principle. For instance, maintaining a fixed sample size regardless of quality changes could lead to unnecessary allocation of resources or oversight of potential issues. Similarly, relying solely on moving averages or the AQL of raw materials may not accurately reflect the product's current quality levels or the variability introduced within the production process. Therefore, adjusting sample size based on observed quality is the most rational and effective strategy in this scenario.