Practice Test Geeks(SPC) Statistical Process Control Certification Practice Test
← All SPC Flashcard Decks

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.

Read the first 7 Process Variation & Capability flashcards as text

  1. Which assumption must be verified before using standard control charts for process capability analysis?

    Answer: The process output must follow a normal distribution

    Standard control charts and capability indices assume process output is normally distributed; non-normal data may require transformations or alternative indices.

  2. A process engineer increases the subgroup frequency from daily to hourly. The most likely benefit is:

    Answer: Faster detection of process shifts and special causes

    More frequent sampling reduces the time between a process shift occurring and its detection on the control chart.

  3. What does a process capability ratio of Cp = 2.0 (Six Sigma level) theoretically yield in terms of defect rate?

    Answer: 3.4 PPM with a 1.5σ shift

    Six Sigma (Cp = 2.0) yields 3.4 PPM defective when accounting for the assumed 1.5σ long-term process mean shift.

  4. In process capability analysis, the 'process window' refers to:

    Answer: The range of values the process naturally produces (6σ spread)

    The process window is the natural tolerance of the process, defined as 6σ (three standard deviations on each side of the mean).

  5. A run of 8 consecutive points all above the centerline on an X-bar chart indicates:

    Answer: A likely shift in the process mean requiring investigation

    Eight consecutive points on one side of the centerline is a standard run rule violation signaling a non-random shift in process location.

  6. Which scenario correctly describes an 'out-of-control but capable' process?

    Answer: A process with Cpk > 1.33 that has a special cause signal on the control chart

    A process can be statistically out of control (special cause present) while still having a Cpk > 1.33, though the instability makes future performance unpredictable.

  7. When comparing Ppk to Cpk for the same dataset, Ppk will typically be:

    Answer: Lower than or equal to Cpk because it uses total variation

    Ppk uses overall standard deviation (larger, including between-subgroup variation), making it equal to or lower than Cpk which uses the smaller within-subgroup estimate.