CQIA Data Collection & Analysis Methods 4 — Questions and Answers
Question 1: Which of the following scenarios represents attribute data rather than variable data?
- Recording the diameter of a machined part to 0.001 inches
- Measuring cycle time in seconds for each transaction
- Classifying invoices as correct or incorrect (Correct answer)
- Weighing packages to the nearest gram
Correct answer: Classifying invoices as correct or incorrect
Attribute data classifies items into categories (pass/fail, correct/incorrect) rather than measuring on a continuous scale.
Question 2: A team notices their process data forms a skewed distribution with a long right tail. Which measure of center BEST represents the typical value?
- Mean, because it uses all data points
- Median, because it is less affected by the tail (Correct answer)
- Mode, because it is the most frequent value
- Range, because it captures the spread
Correct answer: Median, because it is less affected by the tail
In a skewed distribution, extreme values in the tail pull the mean away from the center, making the median a better representative.
Question 3: What is the purpose of a gage R&R study in quality improvement?
- To reduce the number of defects in production
- To evaluate whether the measurement system contributes excessive variation (Correct answer)
- To determine the process capability index
- To set new control chart limits
Correct answer: To evaluate whether the measurement system contributes excessive variation
A gage repeatability and reproducibility study quantifies how much of total variation is attributable to the measurement system itself.
Question 4: On a control chart, what does an upward trend of six or more consecutive increasing points indicate?
- The process is stable and in control
- A potential special cause drifting the process upward (Correct answer)
- Normal cyclical variation in the process
- The control limits need to be recalculated
Correct answer: A potential special cause drifting the process upward
Six or more consecutive points moving in one direction is a trend signal indicating a possible special cause like tool wear.
Question 5: When should a team use a c-chart instead of a u-chart?
- When subgroup sizes vary from sample to sample
- When subgroup sizes are constant and defects per unit are counted (Correct answer)
- When monitoring the fraction of defective items
- When measuring continuous process output
Correct answer: When subgroup sizes are constant and defects per unit are counted
A c-chart is used when the number of defects is counted in constant-size inspection units, unlike the u-chart which adjusts for varying sizes.
Question 6: Which of the following BEST describes the difference between accuracy and precision in measurement?
- Accuracy is consistency; precision is closeness to true value
- Accuracy is closeness to true value; precision is consistency of repeated measures (Correct answer)
- Both terms mean the same thing in quality measurement
- Accuracy refers to sample size; precision refers to scale resolution
Correct answer: Accuracy is closeness to true value; precision is consistency of repeated measures
Accuracy reflects how close measurements are to the true value, while precision reflects how consistently repeated measurements agree with each other.
Question 7: A team collects warranty return data broken down by product line, region, and quarter. Analyzing subsets of this data separately is an example of:
- Benchmarking
- Stratification (Correct answer)
- Normalization
- Triangulation
Correct answer: Stratification
Stratification separates combined data into subgroups by categories such as product line or region to reveal hidden patterns.
