Check Sheet
A check sheet is a simple, structured form for collecting data at the place and time it happens. Each time an event, defect or cause is seen, the person doing the work makes a tally mark in the right box, so counts build up as the work goes on.
It is one of the seven basic quality tools used in Lean Six Sigma projects.
Check sheet is one of seven basic quality tools widely used in lean six sigma improvement projects. It is a handy tool to collect both quantitative as well as qualitative data. When you want to analyze a process, you need to capture real-time data for many different purposes, and a check sheet is built for exactly that. Its format must let you sort each observation into a category as it is recorded. Once you have the data, the next step is to make it visual with a histogram, a Pareto chart or a bar chart, so hidden patterns and the actions to take are easier to see.
What are the types of check sheets?
All check sheets do the same job, turning observations into counts, but the layout depends on the question you are asking.
| Type | What it records | Typical question |
|---|---|---|
| Defect (tally) check sheet | How often each type of defect or problem occurs, often split by day, shift or machine | Which defect happens most often? |
| Defect location (concentration) diagram | A drawing of the product where the inspector marks where each defect was found | Where on the part do the defects cluster? |
| Frequency distribution check sheet | Measurements tallied into value ranges (bins), so the sheet becomes a rough histogram as you fill it in | What shape does the measurement data have, and is it inside the specification? |
| Cause (defect-cause) check sheet | Defects cross-tabulated against a possible cause, such as operator, machine or material lot | Do some defects appear only with one machine or supplier? |
| Checklist (confirmation check sheet) | Whether each required step was done, ticked yes or no | Was every step of the procedure completed? |
How do you make a check sheet?
- Agree on the question. Write down what you want to learn, for example “Which defects cause most of the rework on line 2?” A clear question decides what goes on the form.
- Define every category. List the defect types, causes or value ranges, with a short operational definition of each, so two people would put the same observation in the same box. Add an “Other” row and write down what it was.
- Decide when, where and who. Fix the time period (a shift, a week), the place (the station where the defect is first seen) and the person who records. Record the data at the source, not from memory at the end of the day.
- Design a simple form. Put the categories down the side and the time periods or machines across the top. Leave space for the date, the recorder, the product and the total inspected.
- Test it for a short period. Run it for an hour or a shift. If people hesitate over where to put a mark, sharpen the definitions.
- Collect the data. One mark per observation. Group marks in fives so they are quick to count.
- Total and chart the results. Add rows and columns, then plot the totals as a Pareto chart, histogram or run chart.
Check sheet example: from tally marks to a Pareto chart
The numbers below are illustrative, chosen to show the method; they are not data from a real plant. An inspector on a molding line recorded every defect for one week on the check sheet shown above. The totals, sorted from largest to smallest, give the input for a Pareto chart:
| Defect type | Count | Share of all defects | Cumulative share |
|---|---|---|---|
| Scratch | 25 | 43.1% | 43.1% |
| Sink mark | 14 | 24.1% | 67.2% |
| Flash | 12 | 20.7% | 87.9% |
| Short shot | 5 | 8.6% | 96.6% |
| Wrong color | 2 | 3.4% | 100% |
| Total | 58 | 100% |
Scratches and sink marks together account for two thirds of the week’s defects, so they are where the team should look first. The day columns add a second clue: Thursday had the most defects (14), which is worth checking against what changed that day, such as a new material lot or a different crew. The next step is usually a fishbone diagram or 5 Whys on the top category.
Where does a check sheet fit in DMAIC?
Check sheets are most used in the Measure phase of DMAIC, as part of the data collection plan, to get a baseline of how often a problem happens. They come back in the Analyze phase as cause check sheets that test a suspected cause, and in the Control phase as a daily record that shows whether the gain is holding. Because people classify each observation by eye, it is worth checking that different recorders agree; an attribute agreement analysis does this. Plan how many observations you need with the sample size and sampling guide.
Check sheet versus checklist
The two names are often mixed up. A check sheet collects data: it counts how often things happen so you can analyze them. A checklist confirms that a list of required steps or items was completed, such as a pre-start machine check. A checklist is one type of check sheet, but most check sheets in improvement projects are tally sheets that feed a chart.
Tips and common mistakes
- Vague categories. “Bad finish” means different things to different people. Use specific, defined categories and a picture of each defect if you can.
- Too many categories. More than about ten rows slows recording. Start broad, then split the biggest category in a second round.
- Missing context. Without the number of units inspected you cannot turn counts into rates. Record it on the sheet.
- Recording later. Filling the sheet from memory at the end of a shift loses accuracy. Keep the sheet at the workstation.
- Collecting and never using. Chart the totals and review them with the team, or people will stop filling the sheet in.
Sources and further reading
Method reference: ASQ: Check Sheet.
Frequently asked questions
What is a check sheet used for?
A check sheet is used to collect data in real time at the place where it happens, usually by tally marks, so you can count how often defects, events or causes occur and then chart them.
What are the five types of check sheets?
Common types are the defect (tally) check sheet, the defect location diagram, the frequency distribution check sheet, the cause check sheet and the checklist.
Is a check sheet one of the seven quality tools?
Yes. The seven basic quality tools are the check sheet, histogram, Pareto chart, cause-and-effect (fishbone) diagram, scatter diagram, control chart, and either a flowchart or stratification, depending on the source.
What is the difference between a check sheet and a checklist?
A check sheet counts how often things happen so the data can be analyzed. A checklist confirms that each required step or item was done.
Video on how to use check sheets |
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The other basic quality tools in this guide: Pareto charts.
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