LSS Black Belt · PeopleCert · Control · Bank updated 2026-09-22
LSS Black Belt practice questions: Control
5 free questions from 32 on this area · answer and explanation for each · no sign-up
These 5 questions come from the Control section of our LSS Black Belt bank (32 questions on this area, which carries 20% of the real exam). Every question is original, with the correct answer explained and linked to the source it is drawn from.
Free: 6 questions in study mode, no card. All 32 Control questions and the full LSS Black Belt bank: $15 one-time.
1/5 · Control · easy
In the 5S methodology used to sustain a Lean workplace, which activity corresponds specifically to the fifth S, Sustain (Shitsuke)?
AAssigning a fixed, labeled location for every remaining tool and material.
BCleaning the work area and simultaneously inspecting equipment for early signs of wear.
CEstablishing standardized audit schedules, visual controls, and accountability so the first four S's are maintained without ongoing special effort.
DSorting through items at the workstation and removing anything not needed for the current task.
2/5 · Control
A team is setting up an Xbar-R chart for a filling process. To ensure the chart correctly separates common-cause variation from special-cause (assignable) variation, how should subgroups be formed?
ASubgroups should be formed by randomly selecting units from the full day's production regardless of when they were made, to maximize representativeness of each subgroup.
BEach subgroup should contain measurements taken close together in time or under the same short-run conditions, so within-subgroup variation reflects only common-cause noise while between-subgroup variation can reveal shifts.
CEach subgroup should span an entire shift so that every possible source of variation, including operator and material changes, is captured within the subgroup.
DSubgroup size should always equal the total daily production volume so that control limits are based on the largest possible sample.
3/5 · Control · hard
A team runs a 2^(5-2) fractional factorial design, which is classified as a Resolution III design. What does 'Resolution III' tell the team about the alias (confounding) structure of this design?
ATwo-factor interactions are aliased with other two-factor interactions, but all main effects are completely free of any aliasing.
BNo effects are aliased with each other; a Resolution III design gives the same information as a full factorial with fewer runs.
CMain effects are aliased (confounded) with two-factor interactions, so a significant main effect could actually be caused by an unaccounted two-factor interaction.
DMain effects are aliased only with three-factor and higher interactions, so main effects can be interpreted cleanly even if two-factor interactions exist.
4/5 · Control
A Black Belt is finalizing the Control Plan before handing the improved process over to the process owner. The plan documents the critical-to-quality characteristic, its measurement method, sample frequency, and control chart limits, but contains no documented actions for what to do when the chart signals an out-of-control condition. What is the most significant gap in this Control Plan, and what should be added?
AThe plan is missing a control chart entirely, since sample frequency and control limits alone do not prove a chart-based method was implemented.
BThe plan is missing a response (reaction) plan specifying who is notified, what containment actions are taken, and how root cause is investigated when an out-of-control signal occurs.
CThe plan is missing a cost-benefit analysis proving the measurement system's calibration cost is lower than the cost of producing defects, which must be completed before the process owner can accept the plan.
DThe plan is missing an FMEA risk priority number for each characteristic, without which the process owner cannot formally accept ownership of the process.
5/5 · Control
On an Xbar control chart with valid control limits, an analyst notices that the last eight consecutive subgroup averages all fall above the center line, although none of the individual points fall outside the upper control limit. What is the correct interpretation?
ANo action is warranted until a point exceeds a control limit, because run-length rules apply only to attribute charts, not to variables charts like the Xbar chart.
BThe process remains in statistical control, since the sole criterion for an out-of-control signal is a point beyond the upper or lower control limit.
CThe run of eight points above the center line is itself a special-cause signal (e.g., a mean shift), even though no single point exceeds a control limit.
DThe control limits must have been calculated incorrectly, since a properly centered chart could never produce eight consecutive points on one side.
Answer: C. Control charts are interpreted using both the 3-sigma control-limit test and supplementary run/pattern rules (e.g., a run of eight or more points on one side of the center line), which detect non-random shifts that haven't yet produced a point beyond the limits. Recognizing a run as a special-cause signal — not requiring recalculation of limits and not restricted to attribute charts — is essential for correctly reacting to process changes.
Source: the IASSC Lean Six Sigma Black Belt Body of Knowledge — Control
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