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T.Q. Tools

CAUSE AND EFFECT ANALYSIS (FISHBONE DIAGRAMS)

What is Cause and Effect Analysis?

Cause and Effect diagrams are also known as "Fishbones" (because of their shape) or Ishikawa diagrams (after their inventor, Dr. Kaoru Ishikawa, the Japanese Quality Control Statistician).

Cause and Effect analysis is a systematic way of looking at effects and the causes that create or contribute to specified effects.

The effect being analyzed can be expressed as a problem or as "desired state" and the things that have to be in place for us to get to where we want to be.

A fishbone is an organizing technique for processing lists of ideas into groups to make understanding clearer.

How to Draw a Cause and Effect Diagram

In order to provide a full analysis for any given effect, the causes can be represented on a cause and effect or fishbone diagram such as the one shown (Figure 2) to illustrate the statement "lamp doesn't turn on' and the major possible causes which might explain why the lamp doesn't light. Related causes are grouped together on bones of the fish which have been labelled with the common factor.

Identify the area or "effect" to be analyzed or the desired state to be reached.
Hold a brainstorming session with your team to establish all the major possible causes.
Write the effect/desired state in a box at the end of the main spine of the fishbone. Add several bones, drawn at an angle.
From the results of the brainstorming session form groups of causes under a number of headings comprising the main factors contributing to the effect being analyzed.
On each of the major bones, write the contributory factors which the group consider to be part of each cause.
Then decide whether you need to collect additional data to further understand the relationships of cause to effect.

AN EXAMPLE OF A CAUSE AND EFFECT DIAGRAM

ADDITIONAL TIPS FOR CONSTRUCTING THE CAUSE AND EFFECT DIAGRAMS

It is often the case that the following headings apply:

1. Participation by everyone concerned is necessary to ensure that all causes are considered. Everyone involved, must be free to voice their ideas. The more ideas mentioned, the more accurate will be the diagram. One person's idea will trigger someone else's.

2. Do not criticize any ideas. To encourage a free exchange, write them all down. A brainstorming approach is often appropriate for these early steps.

3. Visibility is a major factor of participation. Everyone in the team must be able to see the diagram. Use large charts, large printing, and conduct the diagram sessions in a well lit area.

4. Group together various causes which have a common theme or link and create a "bone" for each theme.

5. Understand each cause as it is mentioned to ensure its proper

placement on the diagram. Use the technique: Why, what, where, when, who and how.

6. Do not overload any one diagram. As a group of causes begins to dominate the diagram, that group should become a diagram itself.

7. Construct a separate diagram for each separate effect.

8. Circle the most likely causes. This is usually done after all possible ideas have been written up on the Cause and Effect Diagram. Only then is each idea critically evaluated. The most likely ones should be circled for special attention.

9. Create an improvement orientated atmosphere in each session. Focus on how to improve a situation rather than analyzing how it arose.

WHEN TO USE CAUSE AND EFFECT DIAGRAMS

The Cause-and-effect diagram has nearly unlimited application. One of its strongest attributes is the participation and contribution of everyone involved in the subject under discussion. These diagrams are useful whenever a situation needs to be understood fully and the relationship between the various factors involved explored. This might be in the context of solving a problem or understanding all the areas which need to be addressed to make a desirable change take place.

PARETO ANALYSIS

What is Pareto Analysis?

Pareto Analysis is a technique for recording and analyzing information which easily enables the most significant aspects to be identified.

A pattern usually becomes apparent when we look at the relationship between the numbers of Rems/occurrences of any situation and their relation to the "cause" under consideration. The pattern has been referred to as the "80/20 rule" and shows itself in many ways.

Pareto analysis shows at a glance which areas can be regarded as the 'vital few" needing priority measures to tackle them and which are the "trivial many".

The accomplishments of the Pareto analysis are:

Some areas, previously not considered significant, are identified as belonging to the "vital few".
The 'trivial many" are identified: this is not new but the extent is usually surprising.
Priorities are established.

How to Construct a Pareto

Calculate Totals

Taking information from a data or check sheet, list the items in rank order and calculate cumulative percentages. An analysis done in this manner relating to causes of missort mail.

Activity (Failure)	Frequency	% of Total	Cumulative
A. Poorly addressed	11	38	38
B. Wrongly addressed	9	31	69
C. Postroom error	4	14	83
D. Divisional error	2	7	90
E. No address	1	3.4	93.4
F. Item unreadable	1	3.3	96.7
G. Royal Mail error	1	3.3	100
TOTAL	29	100	100

Draw the Pareto Diagram

Draw a bar chart which plots the cumulative percentage against the activities. It may be useful to group minor activities as "others". This is illustrated in the diagram below.

Interpret the Results

The candidates for priority action the 'vital few' will appear on the left of the Pareto diagram where the shape of the cumulative diagram will be steepest. The 'trivial many" should not be ignored however because sometimes what is apparently minor at first can become much more significant at a later date if it is left untreated.

It is important when choosing the data to be charted to have a clear view of the ultimate purpose of the diagram. In the example given above if the purpose was to tackle those areas which most frequently caused failure then the correct data was charted. If the aim was to identify those activities which caused the greatest number of items to be missorted the diagram could be quite different. below illustrates the revised ranking of the categories when this criterion is used:

When to Use Pareto

Pareto can be used to great advantage in many situations where volumes of data exist. It assists with clarifying and prioritizing those aspects which warrant the commitment of resources in order to gain maximum advantage. Its major uses are in frequency based data and tracking that priorities remain the same even when volumes of data available varies widely.

DATA COLLECTION TECHNIQUES

In this section we are going to describe three data collection systems. Data Sheets, Frequency Tables, and Check Sheets.

What are Data Sheets?

Data sheets are used to determine how often an event occurs over a designated period of time. Information is usually collected for events as they happen.

An Example of a Data Sheet

Complaint

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Total

Damaged Mail

111

1111

What are Frequency Tables?

Frequency Tables are used to record the distribution of events within chosen boundaries.

An Example of a Frequency Table

Distribution of the Weight of 120 Students

Class Boundaries (lbs)	Frequencies
109.5 - 119.4	1
119.5 - 129.4	4
129.5 - 139.4	17
139.5 - 149.4	28
149.5 - 159.4	25
159.5 - 169.4	18
169.5 - 179.4	13
179.5 - 189.4	6
189.5 - 199.4	5
199.5 - 209.4	2
209.5 - 219.4	1
TOTAL	120

What are Check Sheets?

Check Sheets are used to record how often an event occurs.

Although the purpose of these techniques is to collect not analyze information, they can often help to indicate an area for action.

EXAMPLE OF CHECK SHEET

TYPES OF TELEPHONE CALL	DEPARTMENT
TYPES OF TELEPHONE CALL	Mails Branch	Personnel	Finance
Customer Query	1111 1111 1111	1111	1111 1111
Wrong Numbers	1111 1	1111	1111 1111 1111
Headquarters		11	1

When to Use Data Collection Techniques

To collect the information needed to analyze the present situation.
To collect information needed to evaluate suggested courses of action.

HISTOGRAMS

What is a Histogram?

A histogram shows the distribution of some characteristic. Because of its immediate visual impact, a histogram is more effective for displaying information than a table.

How to Construct a Histogram

If the data is not already arranged by frequency make a Frequency Distribution Table.
Label the axis "Frequency" and mark values and units on It.
Using the information in the frequency distribution table, construct vertical bars for each of the classes, with height corresponding to frequency.

An Example of a Histogram

When to Use Histograms

When ever appropriate to increase the visual impact of numerical data.

FLOW CHARTS

What are Flowcharts?

Flowcharts show the inputs activities, decision points, and outputs for a given process. There are many variations that have been adapted for specific purposes (eg to show flow of paperwork through an administrative system; to show movement of materials through an operational system).

How to Construct a Flowchart

Flowcharts use standard symbols connected by arrows to show how the system or work process operates. To construct a flowchart, identify the major activities to be completed and decisions to be made as the work process is implemented. Then check the logic of the plan by following all possible routes through the chart to ensure that you have planned for contingencies.

Use the following symbols in drawing a flowchart.

	Statement of Initial input or final output.
	Statement of an activity.
	Decision point.

AN EXAMPLE OF A FLOWCHART

Responding to an HDS Order Enquiry

When to Use Flowcharts

Flowcharts are particularly useful for documenting the steps of a work process either to analyze the current situation or to provide a plan to follow.

GANTT CHARTS

What are Gantt Charts?

A Gantt Chart is a diagram that documents the schedule, events, activities, and responsibilities necessary to complete a project.

How to Construct a Gantt Chart

Although there are many variations, all Gantt Charts document what is to be accomplished, by whom, and when. The steps required to construct a Gantt Chart are:

Break the implementation plan into achievable steps.
Assign responsibility for each step to a team member.
Decide how long each task will take, and set a realistic completion date.
Document the assumptions on which the plan is based, and the contingency plans to implement if those assumptions are not valid.

AN EXAMPLE OF THE USE OF A GANTT CHART

Using a transport project as an example.

SCHEDULE
TASK	ASSIGNED TO	WEEK ENDING
TASK	ASSIGNED TO	1/6	8/6	15/6	22/6	29/6	5/7	12/7	19/7
Liaise with districts	Andrew
Process bids	Helen
Discuss bids with MT	Helen
Discuss van movement	Peter
Deploy vans	Peter and Helen

When to Use Gantt Charts

Gantt Charts are particularly useful when managing a complex multiphased task or where the aim is to optimize the use of resources or manpower.

FAILURE MODE EFFECT ANALYSIS - GUIDELINES

1. List part/process under consideration, e.g. gear.

2. For each part/process list all possible failure modes, e.g. fracture, excess vibration.

3. List possible effects of failure e.g. gearbox failure, increased maintenance etc.

4. List possible causes of failure e.g. material, heat treatment, incorrect gear form etc.

5. Probability factor Assess how likely failure is. Base on reliability data if possible, if not use best judgement.

1 = Failures extremely infrequent.

10 = Failures almost certain to occur.

6. Severity Factor - Assume failure has occurred. Will this have impact on customer? Assume also the customer will get the defect.

1 = Customer will not notice.

10 = Safety of product affected.

7. Detection Factor - What is the probability the customer will subsequently receive the product?

1 = Will not reach the customer.

10 = Customer will receive product.

8. Multiply together to obtain risk factor (improvement weighing).

FAILURE MODE EFFECT ANALYSIS

Part or Process	Potential Failure Mode	Likely Effect of Failure	Cause of Failure	Probability Factor A	Severity Factor B	Detection Factor C	Improvement Weighting AxBxC

IDEA EVALUATION

Purpose

To identify ideas that Problem Solving teams can work on, at different levels in the organization.

Method

Take the brainstorm lists and evaluate and categorize each idea into one of the following groups; mark up the lists with the appropriate capital letter indicated below:

T = Totally within the teams control to work on, and to be able to produce a solution to the problem which is likely to be implemented.

P = Partially controllable within the group, i.e. the team may be able to come up with some solution, but the total problem would probably need the involvement of other departments.

N = Not team controllable are ideas over which the group has no direct control at all, e.g. redesign the building.

During this process ft may be appropriate to cross out any ideas which are totally superfluous.
Take all the T type items and decide which one the team members would like to tackle (note in many cases it will be appropriate to do a data gathering exercise first, to measure which is the most significant problem).

Problem Solving Structure

Problem Solving must be categorized (T, P, N)
Problems should be logged and monitored

PROBLEM SOLVING LOG

ORIGINATOR: REF NO: DIVISION / DEPT: SECTION:	EXTN: DATE:
WHAT IS THE PROBLEM?: CLASSIFICATION: T/P/N
ACTIONEE: AGREED FORECAST COMPLETION DATE: ACTION TAKEN:
SIGNED OFF BY ORIGINATOR:	DATE:

PAIRED COMPARISON

Purpose

To get group consensus on the selection of an item from a list (e.g. which problem shall we tackle?)
To avoid problems with voting systems.

Rules

Each member does his or her own chart.

Method

List all contending items (in any order) on the left.
Compare item 1 with item 2 decide which is the most important and ring the appropriate number in column 1 row 1.
Repeat, comparing item 1 with item 3 etc. and ring the appropriate number in each succeeding column.
Then after item 1 has been compared with all the others, go on to item 2 and repeat the cycle of events until all items have had a paired comparison.
Count up all the ringed '1's on the chart and put the total against item 1. Do this for all the other numbers.
Use the Vote Matrix to record the votes for each item from each member's chart. Add the votes across each row to find out the circle's total score for each item.
The maximum score will identify the major item to look at first.

PAIRED COMPARISON CHART

VOTE MATRIX FOR PAIRED COMPARISONS

No	MEMBER VOTES	TOTALS	RANKING

WHY - WHY DIAGRAM

Purpose

To provide an alternative method of identifying root causes to a problem
To practice divergent thinking technique

Rules

Brainstorm the causes
Identify the major cause

Method

Take a selected cause and use a WHY - WHY diagram to explore the underlying causes of the problem
Each divergent step of the WHY - WHY analysis is produced asking 'why?', see example below
The answers to the question 'why?' are causes of the problem

EXAMPLE OF WHY - WHY DIAGRAM

HOW - HOW DIAGRAM

Purpose

To creatively explore and consider numerous solution alternatives instead of jumping to the 'obvious solution'
Helps members determine the specific steps that should be taken to implement a solution and hence formulate a specific action plan
It helps practice a divergent technique

Method

Begin with a solution statement and explore possible ways of accomplishing the action at each stage by asking 'how' (see example below)
At each stage of the chain a convergent process can be used to narrow the list of alternatives before the next divergent step is taken
Advantages and disadvantages, change of success, and relative cost of each alternative can be established to get a more objective selection process

EXAMPLE OF HOW - HOW DIAGRAM

FORCE FIELD ANALYSIS

Purpose

To evaluate potential solutions to problems.
To identify opportunities for improvement.

Guidelines - To be read in conjunction with diagram on next sheet.

Driving Forces - Promote the solution (activity level).

Restraining Forces - Oppose the solution (activity level).

1. Define the solution (activity level), e.g. automatic heat treatment of gear.

2. Brainstorm the driving forces, e.g. reduction of failures, less preventative maintenance, less failure maintenance, reduced customer complaints, less spares required, etc., and the restraining forces e.g. cost of equipment, maintenance of equipment, specialized application only, etc.

3. Scale and judge the intensity of the forces using scale factor of 1 to 10 for each force, e.g.

Reduction of failures = +8

Less preventative maintenance = +6

Cost of equipment = 7

Specialized application only = 4

4. Add scale factors for driving forces i.e. 33 from diagram on next sheet and, Add scale factors for restraining forces, i.e. 15 from diagram on next sheet.

5. The ratio obtained by dividing the cumulative scale factor for the driving forces by that of the restraining forces i.e. 33 divided by 15 equals 2.2, can be compared with ratios for other potential solutions. The bigger the ratio number, the better the solution.

6. However, improvement action plans can be put in place to improve the ratio for any given potential solution.

7. Force Field Analysis should be repeated to evaluate other potential solutions.

EXAMPLE OF FORCE FIELD ANALYSIS