Practice Test Geeks(SPC) Statistical Process Control Certification Practice Test
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Process Variation & Capability Flashcards

7 cards from real SPC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. A process produces 1,350 PPM defective. What is the approximate process sigma level?

    Answer: 4σ

    Approximately 1,350 PPM corresponds to a 4-sigma process (with a 1.5σ shift assumption used in Six Sigma methodology).

  2. Which chart is most appropriate for monitoring individual measurements when subgrouping is not practical?

    Answer: Individuals and Moving Range (I-MR) chart

    The I-MR chart is used when data is collected one unit at a time and subgrouping is not feasible.

  3. What is the primary reason for collecting rational subgroups in SPC?

    Answer: To ensure variation within subgroups reflects only common causes

    Rational subgroups are designed so within-subgroup variation reflects only common causes, making between-subgroup shifts easier to detect.

  4. If a process has both its mean and standard deviation change simultaneously, which chart would detect this situation most completely?

    Answer: Both the X-bar and R charts used together

    The X-bar chart detects mean shifts while the R chart detects changes in variation; using both together provides complete process monitoring.

  5. A process with high Cpk but frequent customer complaints most likely suffers from:

    Answer: Specification limits set too wide relative to actual customer needs

    If Cpk is high but complaints occur, the specification limits may be wider than what customers actually need, masking true quality problems.

  6. Which term describes the natural, inherent variation in a stable process due to many small, unavoidable causes?

    Answer: Common cause variation

    Common cause variation is the background noise inherent to every process, caused by many small factors that cannot be individually identified.

  7. When a process is 'in statistical control' but not capable, the correct management action is to:

    Answer: Redesign or improve the process to reduce inherent variation

    An in-control but incapable process has stable but excessive common cause variation that requires fundamental process improvement, not reaction to individual points.