7 QC TOOLS

Updated: Sep 11, 2020

1-Stratify data

2-Pareto diagram

3-Cause & effect diagram

4-Histogram

5-Scatter Diagram

6-Check Sheets

7-Control Charts


Will be explained through the creation of a QC Story


QC Story

  • A procedure for problem-solving

  • ‘Story’ means ‘Logical Flow’

QC Story
QC Story

QC Story Steps

1. Define

-Define the problem clearly

  • Demonstrate the importance of the problem

  • Show the background of the problem

  • Explain with data the pain and impact of pain

  • Define the theme with target

  • Form a team and appoint a leader

  • Present and estimated budget

  • Prepare a schedule

2. Observation

  • Investigate data

  • Go to Gemba

  • Observe both conforming and non-conforming products/situations

How to Collect Data


1.Have Clear Defined Objectives

•Controlling and monitoring the production process

•Analysis of non-conformance

•Inspection

2. What Is Your Purpose

•Collecting as per strata

•Collecting in Pairs (correlation)

3. Are Measurements Reliable

4. Find Right Ways to Record Data

•Arrangement

•Data sheet


A-Check Sheet


What

An easy to understand form used to answer the question “How often are certain events happening?”

Why

Starts the process of translating “opinion” into “fact

When

Gathering data in order to detect patterns. Good point to start most problem-solving cycles.

Purpose of Check Sheets

  • Simplification of the data collection process

  • Reduction of recording errors

  • Ease of analysis

How

•Team agrees as to exactly what event is being observed.

•Decide on the time period during which data will be collected. This could range from hours to weeks.

•Design a form that is clear and easy to use making sure that all columns are clearly labeled and that there is enough space to enter the data.

•Collect the data making sure that observations/ samples are as representative as possible.

B-Pareto Principle


VilfredoPareto (1848-1923) Italian economist

20% of the population has 80% of the wealth

  • Juranused the term “vital few, trivial many”. He noted that 20% of the quality problems caused 80% of the dollar loss.

Pareto Analysis


What

A bar chart that helps to prioritize actions by arranging elements in descending order of occurrence. Sorts out the “vital few” from the “trivial many”.

Why

•To prioritize actions needed to solve complex problems.

•To separate important from non-important causes contributing to a problem.

When

•Many factors are impacting a problem.

•Attention needs to be directed only to the few factors that account for most of the problems.

How

•Define a problem and collect data on the factors that contribute to it.

•Historical records generally provide sufficient information.

•Classify the data by type, cost, percent, number of occurrences, or whatever is appropriate for the situation.

•Arrange the data in descending order.


How contd.


•Draw bar graph showing constituent ratio on the vertical axis.

•Connect the cumulative percentage of each bar graph to obtain the Pareto curve.


Stratification

What

Stratification is a statistical technique of breaking down values and numbers into meaningful categories or classification.

Why

To focus on corrective action or identify true causes.

When

To identify the cause of the problem if they come from a particular source.

•To analyze root cause in conjunction with other techniques like Pareto diagram histogram and graphs.

How

Regroup original data as per the source of data(e.g.. Machine wise, shift-wise, model-wise, supplier-wise)

•If required collect data a fresh after making the source from which they come.

•Recreate histogram, Pareto charts, and graphs on classified data

3. Analysis


Find out what the main causes are

Set up Hypothesis

Eliminate irrelevant causes

Brainstorming

Cause & Effect Diagram

Mark those with a higher probability

Cause Effect Matrix

Rating and Ranking

FMEA

Test the Hypothesis

Collect data or conduct experiments to the validated hypothesis

List validated causes

Histograms

Control Charts