Which of the following is NOT a root cause of defects?

In the context of identifying root causes of defects in a system or process, the option indicating "increased training for staff" does not align with typical root causes. While inadequate design, cheap spares, and poor installation practices all represent factors that can lead to defects—such as insufficiently designed components, low-quality replacement parts, or improper handling and installation—all relate directly to systemic issues that can generate faults or failures in a product or system.

In contrast, increasing training for staff is a proactive measure aimed at enhancing understanding and skills among employees. This practice is intended to reduce defects by equipping staff with the knowledge and skills necessary to perform their tasks correctly, thereby improving overall performance and quality. Therefore, it does not constitute a root cause of defects; rather, it serves as a potential solution to address and mitigate existing root causes. By providing more training, organizations can directly improve their processes and reduce the likelihood of defects occurring due to human error or lack of knowledge.