Six Sigma Green Belt Certification 2025 – 400 Free Practice Questions to Pass the Exam

The situation described refers to a Type II error, which occurs when a decision is made to accept a null hypothesis that is actually false. In this context, the store is mistakenly considering defective mattresses as acceptable or "good." This scenario highlights the concept of failing to detect a defect when one truly exists, leading to a situation where defective items are allowed into inventory.

Selecting "Beta" correctly identifies this type of error because it is associated with the probability of a Type II error in statistical testing. Understanding this term is important in Six Sigma practices as it helps in recognizing the potential pitfalls in quality control processes and ensures that defects are not overlooked, which can affect customer satisfaction and operational efficiency.

The other options do not accurately describe the mistake of accepting defective products. Alpha typically refers to a Type I error where a true null hypothesis is rejected, ordinal relates to a level of measurement that indicates order but not the degree of difference, and nominal refers to categorical data without inherent order or ranking. Thus, Beta stands out as the term that directly applies to the concept of failing to identify an existing defect.