Measure Phase: Data Analysis Flashcards
7 cards from real Lean Six Sigma Black Belt Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Measure Phase: Data Analysis flashcards as text
A Black Belt calculates a process sigma of 4.5 using long-term data. What is the equivalent short-term sigma level assuming the standard 1.5-sigma shift?
Answer: 6.0
Adding the 1.5-sigma shift to the long-term sigma of 4.5 gives a short-term sigma of 6.0, which represents the process's best-case capability.
When should an EWMA (Exponentially Weighted Moving Average) chart be preferred over a standard Shewhart X-bar chart?
Answer: When the process produces small, sustained shifts that accumulate over time
EWMA charts give more weight to recent observations and are more sensitive than Shewhart charts for detecting small, gradual process shifts.
In hypothesis testing, what does 'power' (1 - beta) represent?
Answer: The probability of correctly rejecting a false null hypothesis
Power (1 - beta) is the probability that a statistical test correctly detects a real effect and rejects a false null hypothesis.
A stem-and-leaf plot of cycle time data reveals two distinct peaks. What does this bimodal distribution most likely suggest?
Answer: Two different process streams or populations are mixed in the data
A bimodal distribution typically indicates that two distinct populations or process streams—such as two machines or shifts—are combined in the dataset.
What is the primary risk of using a t-distribution instead of a Z-distribution when the sample size is large (n > 120)?
Answer: The results are virtually identical, so the risk is negligible
For large sample sizes, the t-distribution converges to the Z-distribution, making the practical difference between conclusions negligible.
Which graphical tool is most effective for detecting outliers and comparing distributions across multiple groups simultaneously?
Answer: Box plot (box-and-whisker plot)
Box plots display the median, quartiles, and outliers for each group, making them ideal for comparing distributions and identifying outliers across multiple groups at once.
In a Gauge R&R study, the 'reproducibility' component specifically measures variation due to:
Answer: Differences between appraisers using the same gauge on the same parts
Reproducibility is the variation in measurements caused by different appraisers measuring the same part with the same gauge under the same conditions.