Statistical tools

FMEA prioritizes potential failures using the Risk Priority Number (RPN), which is calculated by multiplying severity, occurrence, and detection ratings to highlight the most critical risks. Relying on manager preference or project size is subjective and fails to systematically evaluate actual process vulnerabilities.

A Pareto chart is a bar graph that ranks categories from most to least frequent, helping teams identify the vital few problems that cause the majority of issues. In contrast, variance over time (Option A) is typically analyzed using run charts or control charts rather than a Pareto diagram.

Six Sigma quality represents a statistical target of 3.4 defects per million opportunities, which mathematically translates to 99.99966% defect-free performance. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

• !Option A is incorrect because a 99% defect-free rate actually corresponds to a much lower sigma level of approximately 3.8.
• !Control charts use statistical limits to monitor process stability and detect whether variation is due to common or special causes over time.
• !Option C is incorrect because inventory turns measure supply chain efficiency rather than statistical process capability.
• !Option A is incorrect because asserting that a real difference or effect does exist is the role of the alternative hypothesis.
• !Option A is incorrect because failing to reject the null hypothesis only occurs when the p-value is greater than alpha.

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