CPHQ - Certified Professional in Healthcare Quality Statistical Process Control Questions and Answers

Question 1

A quality improvement team is monitoring the monthly percentage of patients who develop a catheter-associated urinary tract infection (CAUTI). The total number of patient-days varies each month. Which type of control chart is most appropriate for this data?

Accepted Answer

p-chart

Answer

A p-chart is used for attribute data (an event either happened or it didn't) when tracking the proportion or percentage of items with a defect in subgroups of varying sizes. In this case, the 'defect' is a CAUTI and the subgroup size (total patient-days) changes monthly.

Question 2

In Statistical Process Control, what is the primary purpose of calculating and plotting control limits on a chart?

Accepted Answer

To distinguish between common cause and special cause variation.

Answer

Control limits are statistically calculated from the process's own data to define the expected, inherent range of variation (common cause). Data points that fall outside these limits signal the presence of an unexpected, assignable cause (special cause variation) that should be investigated.

Question 3

A quality professional is reviewing a control chart for central line-associated bloodstream infections (CLABSIs). They notice a single data point that falls above the upper control limit (UCL). What is the most appropriate initial interpretation of this data point?

Accepted Answer

The process is exhibiting special cause variation that requires investigation.

Answer

A single point outside the control limits is a primary signal of special cause variation. This indicates that an unusual, non-random event has influenced the process, and the cause should be investigated to understand what happened.

Question 4

Which of the following best describes a process that is considered to be 'in statistical control'?

Accepted Answer

A process where the variation is predictable and consistent over time.

Answer

A process is 'in statistical control' or 'stable' when its variation is due only to common causes inherent in the system. This results in a predictable and consistent pattern of variation over time, even if that performance level is not desirable or meeting external targets.

Question 5

An emergency department is monitoring the number of patient falls per 1,000 patient days. Since the number of patient days (the 'area of opportunity') fluctuates each month, which control chart is the most appropriate for monitoring this rate?

Accepted Answer

u-chart

Answer

A u-chart is used to monitor the rate of defects per unit (e.g., falls per 1,000 patient days) when the size of the subgroup or area of opportunity (the number of patient days) varies over time. A c-chart is used when the area of opportunity is constant.

CPHQ - Certified Professional in Healthcare Quality Practice Test

CPHQ - Certified Professional in Healthcare Quality Practice Test

CPHQ - Certified Professional in Healthcare Quality Statistical Process Control Questions and Answers