Measure Phase and Statistics Flashcards

A normal distribution has 99.73% of data within how many standard deviations of the mean?

Answer: 3

The empirical rule states that 99.73% of data falls within ±3 standard deviations of the mean in a normal distribution.

What does the acronym DPMO stand for in Six Sigma?

Answer: Defects Per Million Opportunities

DPMO stands for Defects Per Million Opportunities and is the standard metric used to calculate sigma level.

In a Gage R&R study expressed as %Study Variation, what threshold is typically considered acceptable for measurement systems?

Answer: Less than 10%

A %Study Variation below 10% indicates an acceptable measurement system; 10-30% may be acceptable depending on context.

Which distribution is most appropriate for modeling the number of defects per unit when defects are rare and independent?

Answer: Poisson distribution

The Poisson distribution models the number of rare, independent events occurring in a fixed interval of time or space.

What is the difference between accuracy and precision in measurement systems?

Answer: Accuracy is closeness to true value; precision is consistency of repeated measurements

Accuracy refers to how close a measurement is to the true value (low bias), while precision refers to how consistently measurements repeat.

A process with Cp = 1.5 but Cpk = 0.8 indicates:

Answer: The process has adequate spread but is significantly off-center

Cp measures potential capability based on spread alone; when Cpk is much lower, the process is not centered between specification limits.

Which continuous probability distribution is symmetric, bell-shaped, and fully described by its mean and variance?

Answer: Normal

The normal (Gaussian) distribution is symmetric and bell-shaped, completely defined by its mean (μ) and variance (σ²).