CPHQ Statistical Process Control 2

Question 1

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?

Accepted Answer

A run rule violation suggesting a process shift

Answer

Eight consecutive points on one side of the centerline is a classic run rule (Nelson Rule 2) indicating the process mean has likely shifted.

Question 2

Which type of control chart is most appropriate for monitoring the proportion of defective items in a healthcare process when the sample size varies?

Accepted Answer

p-chart

Answer

The p-chart monitors proportion defective and accommodates variable sample sizes, unlike the np-chart which requires constant sample sizes.

Question 3

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?

Accepted Answer

42.5 to 57.5

Answer

Control limits are centerline ± 3σ = 50 ± 3(2.5) = 50 ± 7.5, giving limits of 42.5 and 57.5.

Question 4

A hospital tracks medication errors per 1,000 patient-days. Which SPC chart is best suited for this rare-event count data?

Accepted Answer

c-chart or u-chart

Answer

The c-chart (constant area of opportunity) or u-chart (variable area) is appropriate for count data like errors per patient-days.

Question 5

What is the primary purpose of the R chart used alongside an X-bar chart?

Accepted Answer

Monitor process variability within subgroups

Answer

The R chart monitors within-subgroup variability (range), complementing the X-bar chart which monitors the process mean.

CPHQ - Certified Professional in Healthcare Quality Practice Test

CPHQ - Certified Professional in Healthcare Quality Practice Test

CPHQ Statistical Process Control 2