Six Sigma Black Belt Certified Practice Exam

The one-at-a-time approach in experiments tests one factor while keeping all other factors constant. This method can provide insights about the individual effect of each factor, but it inherently misses the complex interactions between multiple factors.

In many real-world scenarios, factors do not operate in isolation; instead, their effects can be dependent on the levels of one another. For instance, the interaction between temperature and pressure could significantly impact the outcome of a chemical reaction, an insight that a one-at-a-time approach may overlook. By ignoring these interactions, you might underestimate or misinterpret the combined effects of different variables, leading to suboptimal decision-making.

In contrast, a full-factorial design systematically investigates all combinations of factors and their levels, allowing for a comprehensive understanding of both individual and interaction effects. This thoroughness is essential for rigorous experimentation, especially in quality improvement initiatives like those pursued in Six Sigma methodologies. Therefore, the key aspect that the one-at-a-time approach is likely to miss is the identification and understanding of these crucial interactions.