Lean Six Sigma Green Belt Certification Basic Statistical Tools 2 — Questions and Answers
Question 1: A dataset has a mean of 50 and a standard deviation of 5. What is the coefficient of variation (CV)?
- 5%
- 10% (Correct answer)
- 25%
- 50%
Correct answer: 10%
CV = (standard deviation / mean) × 100 = (5 / 50) × 100 = 10%.
Question 2: In a normal distribution, approximately what percentage of data falls within two standard deviations of the mean?
- 68%
- 90%
- 95% (Correct answer)
- 99.7%
Correct answer: 95%
The empirical rule states approximately 95% of data falls within ±2 standard deviations.
Question 3: Which measure of central tendency is most resistant to extreme outliers?
- Mean
- Median (Correct answer)
- Mode
- Range
Correct answer: Median
The median is resistant to outliers because it is based on rank order, not the actual values.
Question 4: A process produces parts with diameters measured at 10.1, 10.3, 9.8, 10.5, and 10.3 mm. What is the range?
- 0.5 mm
- 0.7 mm (Correct answer)
- 0.9 mm
- 1.0 mm
Correct answer: 0.7 mm
Range = maximum − minimum = 10.5 − 9.8 = 0.7 mm.
Question 5: What type of data results from counting defects per unit?
- Continuous data
- Attribute data (Correct answer)
- Variable data
- Ordinal data
Correct answer: Attribute data
Counting defects produces discrete attribute (count) data, not continuous variable data.
Question 6: A scatter plot shows points closely clustered around a line sloping downward from left to right. This indicates:
- A strong positive correlation
- A weak positive correlation
- A strong negative correlation (Correct answer)
- No correlation
Correct answer: A strong negative correlation
A downward slope with tightly clustered points indicates a strong negative correlation between the two variables.
Question 7: Which chart is used to display the frequency distribution of continuous data?
- Pareto chart
- Control chart
- Histogram (Correct answer)
- Box plot
Correct answer: Histogram
A histogram displays the distribution of continuous data by grouping values into bins and showing frequency.
Lean Six Sigma Green Belt Certification Basic Statistical Tools 2
A dataset has a mean of 50 and a standard deviation of 5.
What is the coefficient of variation (CV)?