PK0-005 Tools and Documentation Practice Question
A project manager is using a control chart to monitor the number of defects per day. The chart shows 10 data points within the control limits, but all 10 points are above the mean. What does this indicate?
⚠ Common exam trap
The trap here is that candidates mistakenly believe any data point within control limits automatically means the process is stable, ignoring the run rules that detect non-random patterns like sustained shifts above or below the mean.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A special cause variation is likely present
In a control chart, a run of 10 consecutive points above the mean (center line) is a classic indicator of a non-random pattern, even if all points fall within the control limits. This violates the 'run rule' (typically 7 or more points on one side of the mean), which signals the presence of a special cause variation that should be investigated. Option C is correct because the sustained shift above the mean suggests an assignable cause is affecting the process, not random common cause variation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The control limits need to be recalculated
Why it's wrong here
Ten consecutive points above the mean signal a non-random shift, so the limits themselves are not the fault; the process mean has moved. Recalculating limits is the right action when a documented, intentional process change has occurred and the baseline genuinely needs re-establishing, not when detecting an out-of-control run.
- ✗
The process is producing fewer defects than expected
Why it's wrong here
All ten points sit above the mean, meaning defect counts are higher than the process average, not lower. Fewer defects than expected would appear as points below the mean or a downward trend, so this reading inverts the chart's evidence.
- ✓
A special cause variation is likely present
Why this is correct
Ten consecutive points all above the mean constitute a non-random run, which control chart rules flag as special cause variation even though every point sits inside the control limits. It satisfies the stem's scenario of points within limits but consistently shifted.
- ✗
The process is in control and stable
Why it's wrong here
A run of ten points on one side of the mean is a non-random pattern indicating the process is out of control, even though every point sits inside the limits. Stability is claimed only when points vary randomly about the mean with no runs, trends or cycles present.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PK0-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PK0-005 exam.