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Statistical Process Control Flashcards

7 cards from real CPHQ 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 Process Control flashcards as text

  1. Process capability index Cpk differs from Cp in that Cpk:

    Answer: Accounts for process centering relative to specification limits

    Cpk considers both spread and how well the process mean is centered within specifications, while Cp only measures spread relative to spec width.

  2. A healthcare quality team wants to determine if a patient wait-time process is stable before calculating capability. What must they confirm first?

    Answer: The control chart shows the process is in statistical control

    Process capability indices are only meaningful for stable (in-control) processes; an out-of-control process has unpredictable future performance.

  3. Which of the following best explains why using individual (I-MR) charts is appropriate for slow healthcare processes like monthly infection rates?

    Answer: Subgrouping is impractical when data is collected infrequently

    When data is collected too infrequently to form rational subgroups, I-MR charts are used with individual measurements.

  4. A control chart's UCL for an X-bar chart is calculated as X-double-bar + A₂R-bar. What does the constant A₂ depend on?

    Answer: The subgroup size

    The control chart constant A₂ is derived from the expected value of the relative range and varies with the subgroup sample size n.

  5. In SPC, a 'false alarm' (Type I error) occurs when:

    Answer: The chart signals an out-of-control condition when the process is actually stable

    A Type I error (false alarm) in SPC means the chart signals a special cause when in reality the process has not changed.

  6. A hospital's surgical site infection rate is plotted on a p-chart. A new hand-hygiene protocol is implemented. How should the control chart be updated?

    Answer: Split the chart with new control limits calculated from post-intervention data

    After a verified process change, the chart should be split and new control limits calculated from post-intervention data to reflect the new process baseline.

  7. Which statement about the u-chart is correct?

    Answer: It monitors defects per unit when the area of opportunity varies

    The u-chart tracks defects per unit (rate) and is appropriate when the inspection area (e.g., patient-days) varies across samples.