Six Sigma Black Belt Flashcards

A Black Belt notices that a control chart shows 8 consecutive points on the same side of the centerline. According to Western Electric rules, this indicates:

Answer: A special cause of variation

Eight or more consecutive points on one side of the centerline is a Western Electric run rule indicating a non-random (special cause) pattern.

Which type of hypothesis test should be used when comparing the means of two independent groups with unknown and unequal variances?

Answer: Welch's t-test

Welch's t-test (two-sample t-test with unequal variances) is appropriate when comparing two independent group means with unequal variances.

In regression analysis, what does the coefficient of determination (R²) measure?

Answer: The proportion of variance in Y explained by X

R² represents the proportion of total variation in the response variable explained by the predictor variable(s) in the model.

A Six Sigma team wants to prioritize which defect types to address first. Which tool would BEST help visualize the cumulative impact of defect categories?

Answer: Pareto chart

A Pareto chart ranks defect categories by frequency and overlays a cumulative percentage line, enabling the team to identify the vital few causes.

In the context of Lean Six Sigma, what does 'takt time' represent?

Answer: The available production time divided by customer demand rate

Takt time is the available production time divided by customer demand, setting the pace at which products must be completed to meet demand.

Which type of control chart is most appropriate for monitoring the proportion defective when subgroup sizes vary?

Answer: p-chart

The p-chart monitors the proportion (fraction) defective and accommodates variable subgroup sizes, unlike the np-chart which requires constant subgroup size.

What is the primary objective of a Gauge R&R (Repeatability and Reproducibility) study?

Answer: To quantify how much measurement system variation contributes to total observed variation

Gauge R&R separates total measurement variation into repeatability (equipment variation) and reproducibility (appraiser variation) components.