Check Sheets and Types – 7 QC Tools

What is a Check Sheet?

A check sheet is a simple counting tool. It serves as a data-collecting tool used for gathering and visualizing the parameters which are under study. The check sheet is used for almost every industry and process. The check sheet is identified as one of the basic 7 QC Tools. Due to its simplicity, the check sheet is primarily used by the operators or the people who are involved in the work. By collecting data on a check sheet, common patterns and trends can also be identified.

History of Check Sheet

Check sheet concept is nothing new to us. It is derived from the famous tally marking concept used by ancient people. Between 35,000 and 25,000 years ago, in the form of notched bones, tally counting is found to be done in Africa’s Late Stone Age.

Sometimes, a tally marking system was used for numbering also. A technique that has been the sole basis for the shepherds to count their cattle before and after they went for grazing was this tally marking and sometimes stones were used for that.

The counting system had been evolving since then.

Applications of Check Sheet

In Six Sigma, the Measure phase of the DMAIC approach consists of several tools including the check sheet. Sometimes the data collected from the check sheet is used as primary data to understand the problem before initiating the analysis.

In general, the check sheet is used for collecting qualitative data (colors, defect types, names, etc.) and quantitative data (temperature, dimension, weight, etc.). Fig.1- shows an example of a check sheet used for capturing paint nonconformities and Fig. 2- shows an example of temperature measurement.

Figure -1 – Check sheet for paint defects

In Fig2, the scale on the bottom represents the boundaries for each dimension range. Sometimes, instead of writing the actual value, some markings are done as indicated in the figure below.

igure-2- Check sheet for dimensions

The typical types and its uses of check sheets as a part of 7 QC tools are given below,

1. Process distribution check sheet – to understand the distribution and mean of the collected data visually
2. Defective item check sheet – to understand the no. of defectives in a group or sample
3. Defective location check sheet – to identify which location of a product has more defects and the types of defects
4. Defective cause check sheet – to count the maximum no. of causes of a defect

How to Draw a Check Sheet

1. There are no hard and fast rules in designing the check sheets as it is the user’s discretion to use his creativity for better capturing and understanding purpose.
2. You must ensure that it should be user-friendly and, wherever possible, include information on time and location.
3. You should know the type of data you are going to collect and accordingly the check sheet to be designed. Some of the widely used check sheet designs are given below for reference.
4. Also, decide who will collect the date and what time period and how the data will be collected.
5. You can modify the check sheet form for each situation as required by the operation team.
6. Continuously review the check sheet information to redesign for better visualization of contents.
7. The captured data is used for further analysis. If required a secondary check sheet is prepared for collecting based on the output of the analysis.

References:

1. https://en.wikipedia.org/wiki/Tally_marks
2. https://sites.google.com/site/largenumbers/home/1-2/tallies

‘5 Whys Analysis’ a Step-by-Step Guide for Beginners

5Whys Analysis is one of the simple and best tools to identify the root causes of a problem.In this article, we will explore the detailed structure of 5 Whys Analysis, Pre-requisites, Correct usages and its Limitations.

‘5 Whys Analysis’ a Step-by-Step Guide for Beginners

 What is the purpose of 5 Whys Analysis?

Any problems can be addressed with corrections and corrective actions. While corrections deal with mainly on the affected parts, the corrective action focuses on the root cause of the problem. The purpose of asking 5 Whys is to understand the cause of a problem. Causes are required to prevent the occurrences or failures.

For example, a TV manufacturer’s packing team finds a visible scratch on a TV panel in its automatic packing line. Immediately, the scratch is removed by using appropriate surface finishing processes. The actions taken to remove the scratch is called as correction. But the issues not resolved yet.  The reasons for the scratches yet to be identified and to be removed from the process. This will ensure that the same mistake will not repeat. Now, the TV manufacturer’s operation team finds that the scratch happened due to some vibration issues occurred in one of its material handling devices in the automated packing line. Necessary actions taken to minimize the vibration in the device. The actions taken against the cause of the issue is called as corrective action. In this case, the cause is excessive vibration of material handling device. The purpose of 5 Whys analysis is to find out the cause of the problems.

 What is 5 Whys?

5 Whys Analysis is a simple way to ask ‘Why’ 5 times specific to a problem statement, for identification of root cause. For example,

1.   Why the scratch occurred at the TV panel ?

Because, of improper handling by the robotic devices.

2.   Why the improper handling occurred?

Because, the robotic arm was not holding the panel properly, due to vibration.

3.   Why the vibrations occurred?

 Because, the arm bolts were not tightened enough.

4.   Why the bolts were not tightened enough?

 Because the operators were not aware of the tightening torque.

5.   Why the operators were not aware?

Because, maintenance check list not mentioned the required tightening torque of the bolts

By simply asking 5 whys, in this case we could find that the  missing information related to torque requirement in the maintenance checklist has caused the scratches in the TV panel. Hence the corrective action would be revising the maintenance checklist by including torque tightening limits.

 How to use 5 Whys?

There are chances to use the 5 Whys incorrectly. The answers to the preceding questions decide the questions for the succeeding one. Hence, a small misunderstanding, misinterpretation and lack of process knowledge would lead to hide the real causes from our eyes. Following example is one form of incorrect way. For simplification, the example used in the above paragraphs are considered here; 

Sl.	Correct Way of asking 5 Whys	Incorrect Way of asking 5 Whys
1.	Why the scratch occurred at the TV panel ?     Because, of improper handling by the robotic devices.	Why the scratch occurred at the TV panel ? a.       Because, of improper handling by the robotic devices.
2.	Why the improper handling occurred? a.       Because, the robotic arm was not holding the panel properly, due to vibration.	Why the improper handling occurred? a.       Because, the robotic arm was not maintained properly.
3.	Why the vibrations occurred? a.       Because, the arm bolts were not tightened enough.	Why the robotic arm not maintained properly? a.       Because, the maintenance operators were not done their work effectively.
4.	Why the bolts were not tightened enough? a.       Because the operators were not aware of the tightening torque.	Why the operators were not done their work effectively? a.       Because of lack of supervision
5.	Why the operators were not aware?         Because, maintenance check list not mentioned the required tightening torque of the bolts	Why lack of supervision and training observed??        Because, they have not adequately trained.

The table shows that how an analysis changes when the focus shifts from vibration to operators work. It indicates, lack of knowledge and information on the subject can lead us to execute an incorrect 5 Why Analysis. Therefore, while doing the analysis one must take proper care in identifying the questions and to ensure that all the concerned people relevant to the issues are present during the analysis, including the subject matter experts.

Limitations of 5 Whys Analysis

The analysis requires more practical knowledge and experience on the subject. It mainly depends on the person’s skill.

1. There is no assurance that, within 5 Whys one could obtain the root cause of the issue. (Sometimes, it requires less than 5 Whys or some time it would be more)
2. In case of more than one root cause, this 5 Whys Analysis does not always address those causes. It is up to the person who chooses based on his knowledge.
3. The root causes not derived through statistical analysis hence there would be always some subjectivity attached to it.