7 QC tools
Quality control (QC) is?a process through which a business seeks to ensure that product quality is maintained or improved. Quality control requires the company to create an environment in which both management and employees strive for perfection. Quality assurance (QA) is?any systematic process of determining whether a product or service meets specified requirements. QA establishes and maintains set requirements for developing or manufacturing reliable products. TO ensure all quality control process and all quality assurance measures are in place, we often use various tools, ideally to identify, diagnose, measure, compare and take required and accurate preventive and corrective action in time.
Here in this article, the most basic 7 such tools will be discussed.
TOOL-1: Check sheet
-?????????The check sheet is form or data sheet used to collect data in real time at a location where the data is generated.
-?????????Used for:
o??To quantify the types of defects that are occurring
o??To quantify number of defects per type
o??To quantify type and number of defects in each location
o??To keep track of completion of steps in a multistep procedure
Tool-2: Cause & Effect diagram:
-?????????Cause and effect diagram is also known as fish bone diagram or ishikawa diagram. The diagram is look like fish bone. It is introduced by Mr. Kaoru Ishikawa. It identifies many possible causes for an effect or problem and sorts ideas in to useful categories (6M, 5M+1E etc)
-?????????Used for:
o??Identify the possible root cause for any effect problem
o??It is used to structure a brainstorming session
o??Problem to be written on fish mouth
Causes to be written on fish bones in 6 categories
Tool-3: Pareto analysis
-?????????Pareto chart is a type of chart that contains both bars and line graph where individual values and are represented in descending orders by bars and cumulative total are represented by line.
-?????????The chart is named as pareto principle which derived from Vilfredo pareto, a noted Italian economist.
-?????????Pareto chart revolves around the principle of 80/20 rules, where’s underline that, for any process 80% of the problem or failure is just caused by 20% of few major factors which is often referred as vital few, while remaining 20% of problem or failure is caused by 80% of minor issues, often referred as trivial many.
-?????????It is a technique for identifying for vital causes by arranging the data according to the descending orders of their frequency of occurrence.
Used for
o??Distinguish for Vital few and Trivial many
o??Display relative importance of causes of a problem
Helps to focus on causes that will have the greatest impact when solved
Tool-4: Stratification
o??Stratification is a method of dividing data in to sub categories and classify data based on group, division, class or levels that will help in deriving meaningful information to understand an existing problem.
o??The very purpose of stratification is to divide the data and conquer the meaningful information to solve the problem. For example, customer complain may be segregated by
§?Nature of complaints
§?Department responsible
o??Used for
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§?Separate data in to groups and there by draw meaning ful and correct information
§?Diagnose and localize problems
-?????????Example: Supplier wise defects are classified and numbered.
Percentage derived from stratified supplier
Tool-5: Scattered diagram
-?????????It is also called as co-relation diagram.
-?????????It is a graphical presentation of between two variables (or between cause and effect), or between two associated sets of data which occur in pair (e.g. X, Y on from each from each set) using cartesian.
-?????????The scattered diagram displays the pair of data as a cloud of pints. The strength of relationship between the variables (or associated set of data) can be interred from the shape of the shape of the clouds.
-?????????Used for
o??The tool is widely used in statistics and other fields of science and engineering to represent data relationships.
To discover and display relationship between two associated set of data
-?????????Type
o??Strong corelative diagram: is said to exist when value of X increases when Y increases
o??Strong negative correlation: is said to exist when value of X increases when Y decreases.
o??Weak positive correlation: when X somewhat increases as Y increases
o??Weak negative correlation: when X somewhat increases and Y decreases
Tool-6: Histogram
o??Histogram is introduced by Karl Pearson, is a typical bar diagram that represent frequency distribution on each bar or how often each different value in a set of data occurs
o??A histogram is?a bar graph-like representation of data that buckets a range of outcomes into columns along the x-axis. The y-axis represents the number count or percentage of occurrences in the data for each column and can be used to visualize data distributions.
o??Used for
§?Measure the current pattern and extent of variation
§?Assess current conformance to specification and to scope of improvements.
§?Determine whether or not the process is in the state of control
Know the kind of action that will control the process
Tool-7: Control chart
Control chart is also known as Shewhart chart, introduced by Water A Shewhart, or called as process behavior chart, are a statistical process control chart (SPC), tool used to determine if a manufacturing or business process is in a state of control
o??The very purpose of control chart is to determine whether the process is in control, capable under current conditions or out of control
o??Control charts helps in predicting process performance, understand the various production pattern and study how a process changes or shifts from normally specified control limits over a period of times
o??in a control chart, data are plotted against time in X axis, control chart will always have a central line (average or mean), an upper line for upper control limit and a lower line for the lower control limit. These lines are determined form historical data
§?UCL (upper control Limit)
§?CL (Control limit)- process average
LCL (Lower control limit)