Statistical Sampling Flashcards
7 cards from real Quality Auditor 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 Statistical Sampling flashcards as text
A quality auditor wants to estimate the proportion of defective items in a large lot with 95% confidence and ±3% precision. Which factor directly determines the required sample size?
Answer: The estimated proportion and desired margin of error
Required sample size is determined by the estimated defect proportion, desired confidence level, and acceptable margin of error.
In skip-lot sampling, what condition must be met before a supplier qualifies for reduced inspection frequency?
Answer: A specified number of consecutive lots must pass inspection
Skip-lot sampling requires a demonstrated history of acceptable consecutive lots before reducing inspection frequency.
Which sampling method ensures every kth unit is selected after a random start, making it efficient for production-line inspection?
Answer: Systematic sampling
Systematic sampling selects every kth item after a random starting point, making it practical for continuous production.
The operating characteristic (OC) curve for a sampling plan shows the relationship between:
Answer: Lot defect rate and probability of acceptance
The OC curve plots the probability of accepting a lot as a function of the true lot fraction defective.
A process produces 2% defective parts. If a sample of 100 units is drawn and the acceptance number is 5, what describes the probability of rejecting a good lot?
Answer: Producer's risk (alpha)
Producer's risk (alpha) is the probability of rejecting a lot that meets the quality standard (AQL).
When auditing records, a quality auditor uses stratified random sampling by department. What is the primary advantage of this approach?
Answer: It reduces variability within each stratum and improves precision
Stratified sampling improves estimate precision by ensuring each subgroup is adequately represented and reducing within-group variability.
Which statistic measures the spread of the sampling distribution of the mean, and decreases as sample size increases?
Answer: Standard error of the mean
The standard error of the mean equals the population standard deviation divided by the square root of n, shrinking as n grows.
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