IASSC Lean Six Sigma Yellow Belt Practice Questions — 10 Free (2026)

Why are floor markings used to define storage locations and walkways?

• A. Because paint is cheaper than physical barriers
• B. Because the correct condition and any departure from it can be seen without asking ✓
• C. Because the markings prevent equipment from being moved
• D. Because a marked floor is easier to clean than an unmarked one
• E. Because a marked area can be excluded from the site inspection carried out at the end of each quarter

A marked square that is empty when it should be full, or a pallet standing on a walkway, is a deviation anyone can spot from a distance. That is the whole point of making the standard physical rather than written: it removes the need to consult a document or a person. Markings do not stop anything from being moved, and they neither reduce cleaning effort nor exempt an area from inspection. Their value lies entirely in what they let people see. IASSC Lean Six Sigma BOK, 1.4.5

A batch of parts is scrapped after failing a check inside the factory. How is that loss classified?

• A. As a prevention cost, since the parts never reached a customer
• B. As an appraisal cost, because a check was what found them
• C. As an internal failure cost, because the defect was caught before delivery ✓
• D. As an external failure cost, because the material was bought from an outside supplier
• E. As a capital cost, since the material had already been paid for before it was processed

Failure costs are split by who discovers the problem. Scrap and rework found inside the business are internal failures, and this batch never left the site, so that is where it belongs. The check that found the parts is an appraisal cost, but the value of the scrapped material is the failure itself. Prevention covers work done to stop defects arising in the first place, external failure needs the customer to have received the output, and where the material was purchased does not change the classification. IASSC Lean Six Sigma BOK, 1.2.3

What does an executive sponsor provide that no other role can?

• A. A detailed knowledge of how each step of the process operates
• B. The statistical judgement needed to interpret unusual results
• C. The authority and resources that let the work proceed at all ✓
• D. The daily supervision of the team members during the project
• E. The independent verification of the savings that are claimed

A sponsor sits high enough to release people's time, to settle disputes between departments and to make it clear that the work matters. Without that, a team meets a wall the first time the project touches somebody else's area. Detailed process knowledge sits with the operators, statistical judgement with the belts, and independent verification with finance. IASSC Lean Six Sigma BOK, 1.1.6

A team has only 15 readings and wants to see every individual value as well as the general shape. Which display suits that best?

• A. A dot plot showing one mark for each reading ✓
• B. A Pareto chart
• C. A pie chart of the readings
• D. A histogram with bars two units wide covering the full range
• E. A control chart with limits calculated from those fifteen readings alone

A dot plot stacks one mark per reading along a scale, so nothing is hidden and the shape is still visible even with a handful of values. A histogram groups readings into bars, and with only fifteen values the bar heights are unstable and the individual points disappear. Pareto and pie charts are built for categories rather than for measurements. Control limits computed from fifteen points are possible but rest on very little information, and they are not a way of seeing individual values. IASSC Lean Six Sigma BOK, 2.2.4

Which parts should make up the sample for an attribute agreement study?

• A. A mix of clearly good, clearly bad and borderline parts ✓
• B. Only parts that experts have agreed are clearly defective
• C. Only parts taken from the most recent production batch
• D. Parts chosen at random with no verdict established first
• E. Parts kept from an earlier study so results can be compared

The purpose of the study is to find out where judgement breaks down, and it breaks down near the boundary between acceptable and unacceptable. A sample of obvious parts produces flattering agreement figures that collapse the moment a marginal part appears on the line. Every part still needs an established true verdict, otherwise effectiveness against the standard cannot be calculated at all. Reusing an old sample risks inspectors recognising the parts and recalling the verdict rather than judging it afresh. IASSC Lean Six Sigma BOK, 2.3.4

What does drawing a process map in horizontal lanes, one lane per role, add to the picture?

• A. It records how long each of the steps takes to finish
• B. It shows where work passes from one group to another ✓
• C. It ranks the steps by the cost that each step adds
• D. It marks which steps the customer is happy to pay for
• E. It proves which step is the constraint on the flow

Putting each department or role in its own lane makes every crossing of a lane boundary visible, and those crossings are handovers where work waits, information is lost and errors creep in. A team looking for delay often finds it at the crossings rather than inside the steps themselves. Duration, cost and value judgements can be written onto a map as extra notes, but the lanes themselves do not supply them, and identifying a constraint takes data on rates and queues rather than a layout choice. IASSC Lean Six Sigma BOK, 2.1.2

Why can Cpk never come out larger than Cp when both are worked out from the same data?

• A. Because Cp is always worked out from a far larger sample than Cpk can be
• B. Because Cp uses the overall spread of all the data while Cpk uses the subgroup spread
• C. Because Cpk uses only the nearer limit, so any off centring shortens that distance ✓
• D. Because Cpk is always rounded down to the nearest two places of decimals
• E. Because Cp counts both tails of the distribution while Cpk counts one tail twice over

Cp effectively assumes the average sits on the midpoint and gives each side half the tolerance to work with. Cpk drops that assumption and measures the real distance to the nearer limit, and a real distance can equal half the tolerance but never exceed it. The two indices therefore meet when the process is perfectly centred and separate whenever it is not. Sample size, rounding and the choice of spread estimate apply equally to both, so none of them creates the one way relationship. IASSC Lean Six Sigma BOK, 2.4.1

One of the operating rules of kanban forbids a process from passing a defective part to the next one. Why is that rule essential rather than merely desirable?

• A. Because the card would have to be reprinted for the replacement part
• B. Because inspection is cheaper at the end of the line than at that cell
• C. Because the pull signal assumes each container holds only good parts ✓
• D. Because the customer's contract sets a penalty for any late delivery
• E. Because a defect would be found by the next internal audit in any case

The whole loop is sized on the assumption that a container arriving is a container that can be used. A bad part breaks that assumption, so the customer process runs short, calls for stock that was never planned for and either stops or forces someone to hold extra just in case. Since the buffers in a pull system are deliberately thin, quality problems are felt immediately rather than absorbed. Contract penalties and audits are consequences elsewhere, and the cost of inspection is not what the rule is about. IASSC Lean Six Sigma BOK, 5.1.2

Fifty parts were quarantined after a failed check. The response plan says the held material must be dispositioned. What does that require?

• A. The parts are counted and the total is entered in the shift log
• B. The parts are returned to a supplier who provided the material
• C. A decision is made to use, rework or scrap each of those parts ✓
• D. The parts are held until the next audit visit takes place there
• E. The parts are charged against the budget of the project itself

Disposition is the decision about what finally happens to held material, and the choices are to release it, to rework it, or to scrap it, each recorded with the reason. Containment without disposition simply moves the problem into a quarantine area where it accumulates. Counting the parts is a step towards the decision rather than the decision itself. Returning to the supplier only applies if the fault came in with the material, and holding indefinitely or charging the parts to a budget answers nothing about their fate. IASSC Lean Six Sigma BOK, 5.3.3

Why do many programmes keep tracking a project's metric and savings for a year after handover?

• A. Because the accounting year has to be closed before figures count
• B. Because the team is paid a bonus at each anniversary of the work
• C. Because a gain that quietly slips back was never a gain at all ✓
• D. Because the sponsor cannot sign the closure report any earlier
• E. Because auditors insist that all projects be reviewed once a year

Processes drift back towards their old behaviour when attention moves elsewhere, so a result measured in the week of handover proves very little. Continuing to watch the metric after the team has dispersed shows whether the controls put in place are actually holding, and it stops the programme from adding up savings that stopped months ago. The practice is about evidence of durability rather than about audit rules or the accounting calendar. IASSC Lean Six Sigma BOK, 1.3.3