R Programming Language Certification Quality Control & Assurance 2 — Questions and Answers
Question 1: Which R package provides the `qcc` function for creating Shewhart control charts?
- qcc (Correct answer)
- SPC
- controlchart
- MSQC
Correct answer: qcc
The `qcc` package provides the `qcc()` function for Shewhart quality control charts including Xbar, R, S, and p charts.
Question 2: In R's `qcc` package, what does an OC (Operating Characteristic) curve represent?
- The probability of detecting a shift vs. shift size (Correct answer)
- The cumulative sum of defects over time
- The ratio of between-group to within-group variance
- The moving range of consecutive observations
Correct answer: The probability of detecting a shift vs. shift size
An OC curve plots the probability that a control chart will NOT signal an out-of-control condition against various shift magnitudes.
Question 3: What R function from the `qualityTools` package fits a distribution to quality data using maximum likelihood estimation?
- qdist()
- fitdistr() (Correct answer)
- distFit()
- mle.fit()
Correct answer: fitdistr()
`fitdistr()` from the `MASS` package (also accessible via qualityTools workflows) fits distributions by MLE, though `qdist()` is specific to qualityTools.
Question 4: In acceptance sampling using R, what does the 'AQL' stand for in the context of the `AcceptanceSampling` package?
- Acceptable Quality Level (Correct answer)
- Average Quality Limit
- Assured Quality Level
- Acceptance Queue Limit
Correct answer: Acceptable Quality Level
AQL (Acceptable Quality Level) is the worst tolerable process average in a continuing series of lots that is considered acceptable.
Question 5: Which R function calculates process sigma level from a Cpk value?
- sigma_level <- Cpk * 3
- sigma_level <- Cpk + 1.5
- sigma_level <- Cpk * 3 + 1.5 (Correct answer)
- sigma_level <- (Cpk - 1) * 3
Correct answer: sigma_level <- Cpk * 3 + 1.5
The sigma level is approximated as Cpk × 3 + 1.5, accounting for the 1.5-sigma long-term shift assumed in Six Sigma methodology.
Question 6: In R, when using `cusum()` from the `qcc` package, what parameters 'k' and 'h' represent?
- Reference value and decision interval (Correct answer)
- Sample size and subgroup number
- Mean shift and standard deviation
- Alpha risk and beta risk
Correct answer: Reference value and decision interval
In CUSUM charts, 'k' is the reference (allowable slack) value and 'h' is the decision interval threshold for signaling out-of-control.
Question 7: What does the `process.capability()` function in the `SixSigma` R package return that `qcc`'s `process.capability()` does not emphasize?
- DPMO and sigma level (Correct answer)
- Control limits for Xbar chart
- P-value for normality test
- Sample autocorrelation function
Correct answer: DPMO and sigma level
The `SixSigma` package's capability analysis emphasizes Defects Per Million Opportunities (DPMO) and sigma level alongside traditional Cp/Cpk indices.
R Programming Language Certification Quality Control & Assurance 2
Which R package provides the `qcc` function for creating Shewhart control charts?