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
A quality manager notices that 8 consecutive data points on a control chart all fall on the same side of the centerline. What does this pattern indicate?
Answer: A run rule violation suggesting a process shift
Eight consecutive points on one side of the centerline is a classic run rule (Nelson Rule 2) indicating the process mean has likely shifted.
Which type of control chart is most appropriate for monitoring the proportion of defective items in a healthcare process when the sample size varies?
Answer: p-chart
The p-chart monitors proportion defective and accommodates variable sample sizes, unlike the np-chart which requires constant sample sizes.
In a healthcare setting, the standard deviation of a process is estimated from control chart data as 2.5. What is the width of the ±3σ control limits around a centerline of 50?
Answer: 42.5 to 57.5
Control limits are centerline ± 3σ = 50 ± 3(2.5) = 50 ± 7.5, giving limits of 42.5 and 57.5.
A hospital tracks medication errors per 1,000 patient-days. Which SPC chart is best suited for this rare-event count data?
Answer: c-chart or u-chart
The c-chart (constant area of opportunity) or u-chart (variable area) is appropriate for count data like errors per patient-days.
What is the primary purpose of the R chart used alongside an X-bar chart?
Answer: Monitor process variability within subgroups
The R chart monitors within-subgroup variability (range), complementing the X-bar chart which monitors the process mean.
A CPHQ candidate reviews a control chart showing six consecutive points steadily increasing. Which Western Electric rule is violated?
Answer: Six points in a row steadily increasing or decreasing
Six consecutive points trending in one direction (all increasing or all decreasing) violates Western Electric Rule 3, indicating a process trend.
Common cause variation in a healthcare process is best described as:
Answer: Inherent, random variation present in every stable process
Common cause variation is the natural, random variation inherent to a stable process, requiring systemic improvement to reduce.