Qc Tools.docx

QC TOOLs BRAINSTORMING All of the charting techniques are aids to thinking. But another equally important and quite creative tool is coined from the endless source of ideas. The brain. This tool is called Brainstorming.

What is Brainstorming? Explained in its most basic way, it is using a group of people to stimulate the production of ideas. Proven process for producing new ideas and developing creative solutions to problems. Works by focussing on a problem and coming up with as many solutions in as short a time as possible.

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In brainstorming…     



A leader or facilitator takes control of the session, initially defines the problem to be solved & keeps the session on course. Everyone agrees on the question or issue being brainstormed. Ideas are noted on a flipchart or blackboard or recorded on tape to be studied for future evaluation. Sessions are informal, with enthusiastic atmosphere – encouraged as a FUN activity. There is no criticism of ideas. No evaluation of an idea should be made during brainstorming time.

Brainstorming can either be carried out by individuals or groups…… Individual brainstorming 



Tends to produce a wider range of ideas. Individuals are free to explore ideas in their own time without any fear of criticism or feeling domination from other group

members.

Group Brainstorming 

Develops ideas more deeply and effectively, as when difficulties in the development of an idea by one person is reached, another person’s creativity and experience can be used to break them down.

Brainstorming can be used in two ways Structured Every person in a group must give an idea as their turn arises in the rotation or pass until the next round. Unstructured Group members simply give ideas as they come to mind. Things to keep in mind…  

An agenda distributed prior to the meeting will give members a chance to think in advance about the upcoming brainstorming topic. Use very clear and visible writing materials like LARGE SHEETS of paper with bold ink pens or TRANSPARENT SHEETS with Overhead Projectors.

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Blackboards can easily be seen but they get erased. It is better to keep a brainstorming list that can be easily presented to another group of people.

In summary… Expands one’s thinking to include all of the dimensions of a problem or solution. As the human brain’s capacity and limits are as yet unknown then so are the limits for ideas and possible solutions to a problem.

NGT   NGT, Nominal Group Technique, is a weighted ranking technique that allows a team to prioritize a large number of issues without creating “winners” and “losers”.   Tries to provide a way to give everyone in the group an equal voice in problem selection. Seven Steps in Nominal Group Technique (NGT) Process   Have every one on the team write (or say) the problem that he/she feels is most important.   Write the problem statement where the team can seem them.   Check with the team to make sure that the same problem hasn’t been written twice.   If a problem is repeated combine them into one. Ex. 1. Customer Complaints Rises 2. Low Yield at Test We could combine this as “Quality is going down”. 1.

1. Ask the team members to write on a piece of paper the letters corresponding to the number of problem statements the team produced. For example: Problem produced = 5 a. a. Space

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b. b. Safety c. c. Housekeeping d. d. Quality going e. e. No preventive maintenance Each member’s paper would look like this: a. a. _______ b. b. _______ c. c. _______ d. d. _______ e. e. _______ 2.

2.

Vote on which problem is most important.

So if someone thought “quality going down” was the #1 problem, it would look like this: a. a. _____ b. b. _____ c. c. _____ d. d. __5__ e. e. _____ Everyone then has to complete the list by voting what’s second most important, third most important,, etc. 3.

3. Add up each line of numbers across and put them in order. The item with the highest number is the most important one of the total team. For example, the list has already complete and look like this: a. a. 2, 5, 2, 4, 1 = 14 b. b. 1, 4, 5, 5, 5 = 20 c. c. 4, 1, 3, 3, 4 = 15 d. d. 5, 2, 1, 1, 2 = 11 e. e. 3, 3, 4, 2, 3 = 15 On the above example, “B” (Safety) would be the most important item since “B” has the highest points.

4.

4.

You would then work on item B (Safety) first, and then move through the list.

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CHEKCSHEET 

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It is a Quality Control Tool used to present information based on sample observations from a simple listing of items.

Types of Checksheet 

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DEFECT LOCATION CHECKSHEET DATA COLLECTION CHECKSHEET

Who started it? The tool is so simple that we don’t exactly know who invented it. It could be an old initiative. DEFECT LOCATION CHECKSHEET   It is a graphical information used for data collection.   This is a very simple example of providing a clear information of defects to be monitored. DATA COLLECTION CHECKSHEET   This type is commonly used.   This tool is easily understood in question “how often are certain events happening”.   It basically translates opinions/observations into facts.   The defect location checksheet can be used in requisite of data collection checksheet.

When do you use a checksheet?  

 You can use this tool if you need to observe patterns of certain occurrences from a particular event, equipment or person.  You can use this tool if you need to monitor the defect occurrence of a particular administrative error committed by a person which the number of errors committed can also be monitored using this tool. This will allow you to have a clear view of the occurrence and provide detection of a potential problem to occur and prevent the problem from happening. Corrective actions can be immediately carried out.

How do you use the checksheet? A step by step process is described below:

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1st – DETERMINE THE SUBJECT – Will it be an event, equipment or person. 2nd – DETERMINE THE CRITICAL OCCURRENCE(S) WHICH NEEDS TO BE MONITORED0. 3rd – SPECIFY THE TIMEFRAME OF DATA GATHERING. 4th – DRAW THE CHECKSHEET FROM – A table reflecting the agreed subject, critical occurrence(s) and the breakdown of monitoring duration. 5th – ANALYSIIS OF DATA PATTERNS – After data gathering is complete, observe for the trend. Conclusion can be drawn at this point as well as the necessary action(s). IMPORTANT : Such data gathering process given a particular subject can be repeated i.e. extending the duration of data gathering at the discretion of the user.

CAUSE AND EFFECT DIAGRAM “The Ishikawa or Fishbone Analysis” History… Japanese Samurai carried seven tools into battle. After World War II, the Japanese discovered quality as a philosophy for economic recovery. It is cultural that the leaders of the economic recovery sought seven tools to accomplish the economic rejuvenation… and then, the seven old tools were chosen as follows: 1. 2. 3. 4. 5. 6. 7.

1. 2. 3. 4. 5. 6. 7.

Cause and Effect Diagram Histograms Check Sheets Pareto Diagrams Graphs Control Charts Scatter Diagrams

Objectives…    

   

To become familiar with all the steps in doing this problem analysis technique. To realize its applicability in analyzing unexplained “effects” regardless of whether they are undesirable or desirable. To appreciate that “C & E” problem analysis is Participative, Popular and Effective when used in groups. The primary purpose of “Basic Cause and Effect” problem analysis is to help the group solve problems.

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The Cause-and-Effect also referred to as Ishikawa diagram, a tree diagram or fishbone diagram, displays the factors that affect a particular quality characteristic, outcome, or problem. The diagram is named after its developer, Kaoru Ishikawa (1915-1989), a leader in Japanese quality control. An Ishikawa diagram is typically the result of a brainstorming session in which the members of a group offer ideas on how to improve a product, process or service.

Basic Steps in creating a “Cause and Effect” Problem Analysis Step 1. State the Problem An effort should be made to define the problem as precisely as possible.

Basic Cause and Effect Problem Analysis

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The problem is the “Effect” and is written in the Box at the right

Step 2. State the Possible Causes The major groupings for the possible causes that will be identified are determined.

Any number of such grouping is permissible. Although the 4M are quite common. Environment is usually added.

1. Material 2. Man

3. Method 4. Machine Step 3: The Brainstorming Session   

      

All members get involved by participating in a brainstorming session. Brainstorming works best when certain rules are followed. The leader reviews these prior to each session. Each member in rotation is asked for ideas. This continues until all ideas are brought out.

A member may have several ideas are but can offer only one per turn. When no ideas occurs, the member simply says, “Pass”. No idea should be treated as stupid. Ideas are not being evaluated during the brainstorming session. An explosion of ideas is better assured when one approaches his or her thinking in terms of the 5 W’s and 1 H. Exaggeration often adds a creative stimulus to brainstorming. The process is speeded substantially by the leader asking a member to write the ideas as they are given. A member should indicate the major grouping he or she wishes his or her idea included under.

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 

The picture of the completed brainstorming session should show similar ideas together in clumps. Thus it will be simpler to analyze. The brainstorming is over when everybody says, “Pass”. The Cause-and-Effect diagram may look like at that time MANPOWER Lack of Awareness No Insu headcount

Dull STR toolings

MATERIALS Frames

training

Design of Assy Machines are For frames w/ Top Rails MACHINES

Use of M-type wire

have top rail

STR is done after Wire bond

BROKEN WIRE

No monitoring after STR

Non-standard handling practice METHODS

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Step 4: Identification of best ideas    

The ideas collected during brainstorming are critically examined to identify those that are best. Identifying the best causes can be a time-consuming process involving critical analysis of the pros and cons of each. The process can be speeded by giving each members the opportunity to vote for each cause they believe is important. It may not be scientific but experience has demonstrated that it works quite well.

MANPOWER No headcount

MATERIALS Lack of awareness Insu Frames have training top rail

Use of M-type wire

BROKEN WIRE

Dull STR toolings

No monitoring STR is done after STR Design after wirebond of Assy Machines are for frames w/ Non-standard Top Rails handling practice MACHINES METHODS

Step 5: Ranking 

The most probable cause will be ranked in order of importance.

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  

The group looks at those causes that have been encircled. Then voting is done. Members vote only on these encircled major causes. Finally, priority ranking is added beside each of the major causes.

Step 6: Verification     

The most likely cause is tested in an attempt to verify it. The top cause is labeled #1. That is the one the group will want to attempt to verify. Members may suggest a number of common sense of ways to do this but it is appropriate to test the top ideas first. After the true cause has been verified, there is an important follow-up to the causes and the effect problem analysis. The way to get result is to identify problems or objectives; specify the actions needed, state who will follow through and set a target date for completion.

ACTION ITEMS ITEM

ACTION

WHO

DATE TARGET ACTUAL

SCATTER DIAGRAM Scatter diagram is a tool used to see if a relationship appears between two variables.

Why use a Scatter Diagram? 

Scatter diagrams can be used to access the relationship between two variables or characteristics. Are the two variables related?

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

What is the nature of relationship? How strong is the relationship? This may be helpful when investigating the cause of a problem, to help determine whether a particular cause and effect are related, and verify whether a corrective action has had the desired the effect.

How Does a Scatter Diagram Looks Like?

% d e f e c t i v e i n

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Cutting oven conveyor speed setting

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How to construct a Scatter Diagram 1.

Check and decide on the variables, or cause and effect pair, you want to test. MAN

OPERATOR FORGOT TO LOAD THE UNITS INTO THE CURING TIME

MACHINE

INSUFFICIENT CURING TEMP

INSUFFICIENT CURING TIME Mismatch bet. Temp setting & actual and set Temp

Busted Temp Sensor/Controller

High Conveyor Speed Setting

Break-up with BF(?)

Mark Permanency Defect

EXPIRED INK Did not comply to First InFirst Out Use Rule

EXPIRED INK Did not comply to First In-First Out Use Rule

MATERIALS

METHOD

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1. 1. Either use existing data or design a checksheet to collect the data. If possible and when applicable, collect 50 to 100 paired samples. % Defectives in a lot (MPT) Conveyor Speed Run # 1 Run #2 Setting 20 30 40 50 60 70 2. 2. Draw the diagram

% d e f e c t i v e

Mark Permanency Defect Data taken in MPT performed after mark curing 40% 35% 30%

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Determine the scales you are going to use and draw the axes of the graph to suit the minimum and maximum values of each variable. If possible make the axes about the same length. Usually the x-axis (horizontal) is used for the ‘cause’ and the y-axis (vertical) for the ‘effect’. Plot the data on the diagram, marking the points. If values are repeated it is usual to indicate this by drawing the concentric circles about the points. Label the axes and give the diagram a title. The title should include the source of data, a date and the name of the person or team responsible.

WARNING!!! Scatter diagrams can sometimes be misleading in suggesting that there is a causal relationship between two factors being investigated: a relationship may exist but it may not be directly causal/ Moreover, when a relationship does exist it may sometimes not be apparent because the other, and greater, causal or random factors are obscuring it.

A SCATTER DIAGRAM CANNOT PROVE THAT ONE VARIABLE CAUSES ANOTHER – IT MERELY HIGHLIGHTS WHETER A RELATIONSHIP EXISTS AND THE STRENGTH OF THAT RELATIONSHIP.

Interpreting a Scatter Diagram If the value of one variable appears to affect the value of another, there is said to be a relationship between them

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NO CORRELATION

E F F E C T

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POSITIVE CORRELATION

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CAUSE

E F F E C T

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NEGATIVE CORRELATION

           

       

E F F E C T

CAUSE

CAUSE

 

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CAUSE AND EFFECT are unrelated

CAUSE AND EFFECT increase together

“STRONG” CORRELATION

E F F E C T

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          

increase in CAUSE will cause a decrease in EFFECT “WEAK” CORRELATION

 E F F E C T

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CAUSE

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CAUSE

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 

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Data points are closely Clustered together

% d e f e c t i v e

data points are closely clustered together

Mark Permanency Defect Data taken in MPT performed after mark curing 40% 35% 30%

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The graph indicates a strong positive correlation between the conveyor speed and the Mark Permanency % defectives on ink marked devices. As the conveyor speed is increased, the lot % defective also increases. Line of best fit You can draw a line of best fit through the data points on the diagram. This line can be used to make specific cause/effect predictions but ONLY if you are sure the relationship is genuine. To draw the line: 1. 1. Place a transparent ruler parallel to the X-axis so that half the points are above the line. Draw the line here. 2. 2. Place the ruler parallel to the Y-axis and do the same. 3. 3. Mark the point where the lines cross and put your ruler on this point, rotation if until you again have the same number of point on each side. When you have done this, draw the line you have found.

RUN CHART/TIME PLOT/TREND CHART  

 

Run charts are the simplest too construct and use. Run charts are used to analyze processes according to TIME or ORDER.

KEY TERMS Trends   Population  Sample  Runs 

 

Trends are patterns or shifts according to time. Feature the continued rise or fall of a series of points.



A population is the entire data set of the processes.

 A sample is a subgroup or small portion of the population that is examined when the entire population can not be evaluated. 

Runs are patterns in a Run Chart within which a number of points lie on only one side of the central line.

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When to Use a Run Chart?   

History

  

You use a Run chart when you want to understand the trends in data. When you want to identify meaningful shifts in the average of data collected over specified time. Also, use Run Chart when you want to:

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manage performance convert to measures analyze a process visually present data

Run Charts originated from Control Charts. It was Walter Shewhart who initially designed the Control Charts. Run Charts evolved from these Control Charts. But Run Charts focus more on time patterns while a Control Chart focuses more on acceptable limits of the process.

How to construct a Run Chart Step 1. Gathering Data Ex: Yield, Scrap, No. of Claims, Machine Downtime Step 2. Organizing Data - Determine values for y-axis - Determine values of x-axis Step 3. Charting Data - Draw vertical axis - Draw the x-axis - Plot the data - Label - Connect the data Step 4. Interpreting Data

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Trends in the chart Observations from each time interval are consistent Cyclical patterns in the data

Example: Problem Scenario You have just move into a new area that you are not familiar with. Your desire is to arrive at work on time, but you have noticed over your first couple of weeks on the job that it doesn’t take the same amount of time each day of the week. You decide to monitor the amount of time takes to get to work over the next four weeks and construct a run chart. Step 1: Gathering Data Collect measurements each day over the next four weeks. Organize and record the data in chronological or sequential form. Week 1 Week 2 Week 3 Week 4

M 33 35 34.5 34

min/day T 28 30.5 29 29.5

W 26.5 28 28 27

Th 28 26 26 27

Step 2: Organize Data Determine what values for the x (time, day of the week) and y (data, minutes to work) axis will be. Week

1

2

3

4

Day

Travel Time (min) 33 28 26.5 28 36 35 30.5 28 26 25.5 34.5 29 28 26 25 34 29.5

M T W Th F M T W Th F M T W Th F M T

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F 26 25.5 25 25.5

W Th F

27 27 25.5

Step 3: Charting Data Plot the y values versus the x values by hand or by computer using the appropriate scale. Draw horizontal or vertical lines on the graph where trends or inconsistencies occur.

Minutes to Work

Arriving to Work on Time 40 35 30 25 20 M

T

W Th

F

M

T

W Th

F

M

T

W Th

F

M

T

W Th

F

Days of the Week

Step 4: Interpreting Data Interpret results and draw any conclusions that are important. You allow more time to prepare on Monday and the least time during Friday.

Uses of Run Chart   More information can be derived from Run Charts.   A Run chart can provide:   information about favorable shifts in activity   used to monitor a process   information about unfavorable shifts in activity

PIE CHART Pie Charts are simply graphs in which the entire circle represents 100% (not 360 degrees) of the data to be displayed. The circle or pie is divided into percentage slices that clearly show the largest shares of data.

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When to use a Pie Chart? -

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Summarize the results of data collection efforts. Illustrate the results of data collection exercise. Organize your data into an understandable and compelling form. Manage performance. Analyze the current process. Design an improved process.

How to effectively make a Pie Chart? 1. 2. 3. 4.

1. 2. 3. 4.

Tabulate data (if necessary) Label the chart according to what it depicts as a whole. Label each axis according to what it represents and include its units of measure. Indicate the legend.

Course # of graduates

EE 20

CompE 312

ChE 189

ECE 268

IE 176

Engineering Graduates (SY 2000) ME CE 8% 9%

IE 15%

EE 2%

EE CompE 27%

CompE ChE ECE

ECE 23%

IE

ChE 16%

ME CE

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ME 88

CE 103

PARETO CHART -

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Special form of vertical bar graph. Helps determine which problems to solve in what order. Helps direct the attention and efforts to the truly important problems. Gain more by working on the tallest bar rather than tackling the smallest bar.

History Pareto Chart got its name from an Italian economist VILFREDO PARETO on his observations than a relative few people held the majority of the wealth in Milan (1848 – 1923). He triggered alarm by graphically depicting the disproportionate distribution of wealth between the various social classes. Those who talk about the 80-20 rule are referring to the concept of the “major few and trivial many” for example, 80% of defect may be made by 20% of one process alone. Or, 80% of the office errors may be made by 20% of the employees. Or 80% of the scrap may be generated by 20% of the work force.

Steps in constructing a Pareto Chart -

The time period over which data is to be collected must be determined. Although it may be only a few hours, it may require days or even months. What data is to be gathered must be decided. Careful consideration at this time will better assure a minimum of trouble later. A form must be designed for use in collecting the necessary data called the checklist.1 It should be general enough to allow the information to be arranged in a variety of ways in case the first one selected fails. The data is recorded in the checksheet. This will be used to construct the Pareto Chart. Defects Assy Related Test Handler Fab Rtld

1 20 7 6

Week 01 2 25 3 7

3 30 5 2

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TOTAL 75 15 15

Product Related EPC/IPC

1 0

2 1

2 1

5 2

This is the result - a complete Pareto Chart wit the column arranged, as usual, in descending order. 80 60 40 20 0

sy As

l. . Re

. s Te

er dl n a tH

b Fa

ld Rt

tld tR c u od r P

C EP

/IP

C

We can now construct the cumulative line or cum line. Starting at zero, the cum line is extended to the top right hand corner of the first column. It is now at 67 level.

Uses of Pareto Chart    

   

Highlights the number one problem and with visual impact. The best way to assess the current situation by focusing. Efforts is focused in finding greatest potential weakness. Cum line could help in measuring the impact of improvement by comparing current situation and before.

FLOWCHART When you need to identify the actual ideal paths that any product or service follows in order to identify deviations, then FLOWCHARTING is one of the best QC tool to be used.

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What is a Flowchart? A flowchart is a pictorial representation showing all the sequential steps of a process.

History Flowchart was first introduced in 1947 by H.H. Goldstine and J. von Neumann in an attempt to represent algorithms in a precise notation that would be at a higher level than the machine language. Flowcharting uses easily recognizable symbols to represent the type of processing performed.

Here are the five (5) basic symbols:

TERMINAL

F L O W L I N E

PROCESS CONNETOR

DECISION

The oval is the terminal symbol and is used to represent the beginning or end of program (or subprogram) execution. It is used to show the materials, information or actions (inputs) to start the process or to show the results at the end (output) of the process. The box or rectangle is used to show a task or activity performed in the process. Although multiple arrows may come into each box, usually one output or arrow leaves each activity box.

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The diamond shows the points in the process where a yes/no questionnaire is being asked or a decision is required. The circle with either a letter or number is the connector symbol and identifies a break in the flowchart and is continued elsewhere on the same page or another page. The arrow, or flow line is used to indicate flow and direction of the process.

Structured Flowcharts

A. SIMPLE SEQUENCE

B. TWO – WAY SEQUENCE

C. TEST – AFTER LOOP

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D. TEST – BEFORE LOOP

SURVEY AND INTERVIEW Survey is a method of primary research. It is basically gathering and determining certain types of information by asking questions.

Survey Information Includes    

   

Personal data Opinions Evaluations Other info necessary to plan for experiment or an observation or to supplement or interpret the data that result

Considerations in Making a Survey   

  

The survey format The matter of delivery Whom to survey

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questions can range from spontaneous inquiries to carefully structured interrogations.

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the questions can be posed in a personal interview, asked over the telephone, or presented in printed from (questionnaire)

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you may not reached all the people involved, thus you have to select a sample of respondents who represent the group as whole as accurately as possible

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The survey format

The matter of delivery Whom to survey

Sampling generally used for economy and practicality it has to be representative of the whole group and errors should be reduced through the following techniques:

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Probability Sampling - based on chance selection procedures where every element in the population has a probability of selection. The types include: a. a. random sampling b. b. stratified sampling c. c. systematic sampling d. d. area or cluster sampling

Random sampling -

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the samples are chosen in no particular order

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the population is subdivided into subgroups and random selection is done per subgroup

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selections are taken at constant intervals from a list of the population

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draw items from the subject group in stages and select randomly at each stage

Stratified random sampling Systematic sampling Area of cluster sampling Non-probability Sampling Based on an unknown probability of any one of the population being chosen. The types include: - convenience sampling - quota sampling (controlled sampling) - referral sampling Convenience sampling - the members are chosen because the are convenient and economical to reach Quota sampling - set quotas for each characteristics in the population, then select items randomly within each quota Referral sampling - members are identified by others from a random sample, used for small or hard-to-reach groups

The Questionnaire A basic tool of survey and interview. It is an orderly arrangement of questions, with appropriate spaces provided for answers.

Constructing the Questionnaire

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1. 2.

3. 4.

5.

6.

7.

1. Avoid leading questions. Is LM line your favorite process line? What is your favorite package? 2. Make the questions easy to understand. Do you monitor your products regularly? (“regularly” could mean different things to different people) How often do you monitor your products? 3. Avoid questions that touch on personal prejudice or pride. How much is your income? Is your income less than 10K, between 10 – 20K, 21, 30K, or over 31K? 4. Seek facts as much as possible? Which product types failed regularly? (with the word “regularly”, the question is seeking opinion instead of facts) Which devices failed this month? 5. Ask only for information that can be remembered. The following are likely to be remembered. - recent events - significant events may be remembered over long period of time (i.e. the data when you are promoted GM) - insignificant facts may be remembered over time through association with something significant (i.e. it’s not easy to remember what you ate for lunch a year ago but you may still remember because it was the date of the ISO9002 audit) 6. Plan for the physical layout foresight - the design of the questionnaire should be planned to facilitate recording, analyzing, and tabulating 1. 1. Answers should be allowed sufficient space for recording. 2. 2. Adequate space for identifying and describing the respondent should be improved. 3. 3. The best possible sequence of questions should be used. Some questions must precede others because they help explain the others. 7. Use scaling when appropriate

Example:

What is your opinion on the new working hours scheme? Strongly Moderately Mildly Neutral Mildly Oppose oppose oppose favor favor

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Moderate favor

Strongly

8.

8. -

Select the manner of questioning You should select the way that in your unique case gives best sample, lowest cost, lowest cost and best results. The primary ways are: 1. 1. by personal (face-to-face contact) 2. 2. by telephone 3. 3. by mail 9. 9. Developing a Working Plan - For a written survey for example, you need to develop an explanatory message that moves the subject to respond, tells them what to do, and answers all the questions they are likely to ask. 10. 10. Conducting a pilot study - Pilot study is a small-scale version of the actual survey. - Before doing the survey, conduct a pilot study on your questionnaire and working plan. - The purpose is to test what you have planned and improve it based on the pilot study’s results.

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