7 QC Tool

Hi friends!   Today we will learn about the 7QC tools.  These tools are used to collect the information about the problem and hence one can easily identify the problem area. Application of these tools are widely used in manufacturing/ Services/ Medical/Telecom industry across the globe. Once the problem is identified then the root cause of that problem need to be brainstormed.

7 QC tools are listed below.

1. Check sheet
2. Scatter Diagrams
3. Cause-and-effect diagram
4. Pareto Charts
5. Histograms
6. Control chats
7. Flow chats (Process Flow Diagrams)

Check sheet –    It is used to collect the data in desired format and extract the information based on feed data. Suppose ABC is a vehicle garage. If any vehicle comes to a garage for general repairing, then the vehicle needs to be checked by the inspector. The Inspector will prepare a Vehicle Breakdown maintenance Check Sheet for checking the condition of vehicle as shown in below table.  

Scatter diagrams: A graph of the value of one variable vs another variable. It is used to observe the strength of relationship between two variables. A correlation coefficient measures the strength of that relationship. Different types of correlations are shown in below picture

Cause and Effect diagram – This tool is used to demonstrate causes of problem and its effect. Probable causes of any problem can be computed in 5 headers like Man, Machine, Method, Material, and Environment as shown in the picture below. We can also add sub causes of probable cause in this diagram. This is also known as Fish Bone Diagram.

Pareto Chart –

A graph to identify and plot problems or defects in descending order of frequency. So, based on graphical represent we can quickly identify the major problem/ defects.

It is also called 80 -20 rule that means 80 percent of problems happen due to 20% causes. This is a very fundamental and widely used tool in TQM initiative like Quality Circle, Lean Six Sigma, TPM SGA etc.

Let us understand with an example. 

Suppose XYZ is a coffee shop where hot coffee is served to the customers. Among these customers few  complains as well.  Say 20 complaints have been registered in last two months. 

Sl No	Problem	No of complaints
1	Coffee was not tasty	8
2	Coffee was not as hot as per customer requirement	5
3	Wrong order placed to the customer	3
4	Delayed coffee service	2
5	Waiter behavior issue	2

Histograms – A distribution showing the frequency of occurrences of a variable. This is widely used in Six sigma project.

What to observe?

Shape – symmetric or not

  Spread – flatness/variation is small or large

Control charts – A chart with time on horizontal axis to plot values of a statistics. With the help this tool we can easily identify the outliers present in the process. After analysis of outliers, we can find out the root cause of outliers.

Flow Chat or Process Flow Diagram – A chart that describes the steps in a process. With help this tool anyone can easily understand entire process of manufacturing, Service, and project plan etc.