CPHQ Statistical Process Control 4

Question 1

When plotting an Individuals (I) chart, the moving range is typically calculated using how many consecutive observations?

Accepted Answer

2 consecutive points

Answer

The moving range in an I-MR chart uses successive pairs of two consecutive observations to estimate short-term process variation.

Question 2

A CPHQ exam scenario describes a Sigma level of 4.0 for a medication dispensing process. Approximately what percentage of outputs fall outside specification limits?

Accepted Answer

0.62%

Answer

A 4-sigma process has approximately 0.62% of outputs outside specification limits (6,210 DPMO), reflecting high but not Six Sigma quality.

Question 3

A quality team observes that all 15 consecutive points on a control chart fall within the 1σ zone of the centerline. Which pattern does this represent?

Accepted Answer

Stratification, suggesting data from multiple process streams is mixed

Answer

Fifteen consecutive points within 1σ (Western Electric Rule 5) suggests stratification—data is likely sampled from different sub-populations with different means.

Question 4

For the CPHQ exam, which measure is used as the centerline of an R chart?

Accepted Answer

Average of subgroup ranges (R-bar)

Answer

The centerline of an R chart is R-bar, the average of the subgroup ranges collected during the baseline period.

Question 5

A healthcare quality director wants to assess long-term process performance. Which capability metric should she use?

Accepted Answer

Pp, based on total observed variation

Answer

Pp (and Ppk) use total process variation (overall standard deviation), reflecting long-term performance, while Cp/Cpk use short-term within-subgroup variation.

CPHQ - Certified Professional in Healthcare Quality Practice Test

CPHQ - Certified Professional in Healthcare Quality Practice Test

CPHQ Statistical Process Control 4