the seven old quality control tools

7/27/2019 The Seven Old Quality Control Tools

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THE SEVEN OLD QU LITY CONTROL TOOLS


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7 OLD QCT

Cause-and-effect diagram (also known as

the " f ishbone" or Ish ikawa diagram)

Check sheet

Control chart

Histogram

Pareto chart

Scatter diagram

Stratification (alternately, f low chart o r run

chart)


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CAUSE-AND-EFFECT DIAGRAM

FISHBONE DIAGRAM)


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WHEN TO USE A FISHBONE DIAGRAM

When identifying possible causes for aproblem.

Especially when a teams thinking tends to

fall into ruts


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CHECK SHEET


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WHEN TO USE A CHECK SHEET

When data can be observed and collected repeatedlyby the same person or at the same location.

When collecting data on the frequency or patterns ofevents, problems, defects, defect location, defect

causes, etc. When collecting data from a production process.


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CONTROL CHART


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WHEN TO USE A CONTROL CHART

When controlling ongoing processes by finding andcorrecting problems as they occur.

When predicting the expected range of outcomesfrom a process.

When determining whether a process is stable (instatistical control).

When analyzing patterns of process variation fromspecial causes (non-routine events) or commoncauses (built into the process).

When determining whether your quality improvementproject should aim to prevent specific problems or tomake fundamental changes to the process.


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STRATIFICATION


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WHEN TO USE STRATIFICATION

Before collecting data.

When data come from several sources orconditions, such as shifts, days of the week,suppliers or population groups.

When data analysis may require separatingdifferent sources or conditions


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HISTOGRAM


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WHEN TO USE A HISTOGRAM

When the data are numerical. When you want to see the shape of the datas

distribution, especially when determining whether theoutput of a process is distributed approximatelynormally.

When analyzing whether a process can meet thecustomers requirements.

When analyzing what the output from a suppliersprocess looks like.

When seeing whether a process change has occurredfrom one time period to another.

When determining whether the outputs of two ormore processes are different.

When you wish to communicate the distribution of

data quickly and easily to others.


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PARETO CHART


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WHEN TO USE A PARETO CHART

When analyzing data about the frequency

of problems or causes in a process.

When there are many problems or causes

and you want to focus on the most

significant.

When analyzing broad causes by looking

at their specific components.

When communicating with others about

your data


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SCATTER DIAGRAM


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WHEN TO USE A SCATTER DIAGRAM

When you have paired numerical data.

When your dependent variable may have multiplevalues for each value of your independent variable.

When trying to determine whether the two variablesare related, such as

When try ing to ident i fy potent ial root causes o f

problems.

After brainsto rm ing causes and effects u sing a

fishbone diagram , to determine ob ject ively whether apartic ular cause and effect are related.

When determ ining whether two effects that appear to

be related both occu r with the same cause.

When test ing fo r autoc orrelation before constru ct inga control chart.


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QUERIES

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TH NK YOU

the seven old quality control tools

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