CHAPTER 10 - Quality Control

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QUALITY CONTROL


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1. Define quality

2. Importance of quality

3. Objective of quality management4. Quality dimensions and determinants

5. Total Quality Management (TQM)

6. Quality control tools

7. Identify costs of quality

8. Characteristics of inspections


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Quality management is very important agendato the most of organizations. Quality practice

includes everything for example beside theeffective operating schedule, leadership,training and mission also included in qualitymeasurement.

In operation part process of qualitymeasurement is based on statistical processcontrol.


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Quality is defined as meeting or exceedingcustomer expectations that varies. It is the

ability of the total features and characteristics ofa product or service to satisfy given needs.

@Quality is defined as a measure of how closelya good or service to conforms to standards andspecifications. The extent goods or servicesmeet customers satisfaction.


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1. Implications of the quality definition

2. Definition of quality management

3. Definition of quality control


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a) Costs and market share

- Improve market share and provide profitability by providing superior quality

goods and services can gain market share from competitors that provide

lower quality products.

b) Companys reputation- Quality is used as one of the company competitive weapon to distinguish

themselves from their competitors.

c) Product liability

Consumers usually prefer to purchase goods or services that provide the

maximum quality they can obtain per Ringgit in the price range they are willingto spend on.

d) International Implications

- Quality is used to attract domestic and international customers. Establish

brand have the power of branding itself.


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1. To ensure that the goods or specifications

conform to standards or specifications.

2. To minimize demand for the production costassociated with poor quality

3. To ensure there is continued demand for the

companys products and services

4. To assure certain product requirements meetsthe specific standard

5. To struggle for defects free in production.


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Product quality Service Quality


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1. Performance

- The basic operating characteristics of a product or how

well the product or service performs the customers

intended use. For a personal computer, performancecharacteristics would include operating speed and

random access memory (RAM) capacity.

2. Conformance

- the degree to which a product meets design

specifications for example, car matches manufacturers

specification.


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3 Durability- It relates how long the product lasts: its lifespan before replacement; the useful life of the product or service.

4 ServiceabilityIt about the speed, cost, and convenience of repairs and maintenance.How well the manufacturers or service providers handle complaints,the ease of getting repairs, the speed of repairs, and the courtesy andcompetence of the repair person.

5 Aesthetics/ AppearanceHow a product looks, feels, sounds, smells, or tastes for exampleexterior and interior design of a car.


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6 SafetyHow well the product protects users before, during andafter use. It is about assurance that the customer will not

suffer the injury or harm from a product or service, anespecially important considerations for automobiles.

7 ReliabilityIt relates to the probability that a product will operateproperly within an expected time frame such as infrequentneeds for car repairs.


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1. Tangibility- Physical appearance of facility, equipment, personnel and communication materials. Eg. Uniform

a restaurant staff wears . McD and KFC

2. Convenience

-Avaibility and accessibility. Eg: ASTRO service agent

3. Reliability

- Ability to perform a service dependably, consistently and accurately. Eg:

Maybank online banking.

4. Responsiveness

-Willingness of service providers to help customer. Eg: length of time it take

to receive return call on a complaint


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5. Time-Service delivered

6. Assurance

- Knowledgeable personnel and their ability to convey trust and

confidence.

7. Courtesy

- The way customer a treated by employees who come into

contact with them. Eg: politeness, respect, consideration and

friendliness.


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1. Quality of design

- refers to the intention of designers to include or exclude certain features in a product or

services today.

2. Quality of conformance

- refers to the degree to which goods and services conform the intent of the designers.

3. Ease of use and user instructions

- customers or users must be clearly informed on what they should or should not do with a

product so that the product will be used for its intended purposes and in such a way it will

continue to function properly and safely.

4. Service after delivery or post sale service- It consists of all the issues that arise after the product has been purchased. Since products

do not always performs as expected, and services do not always yield the desired results, the

ease of getting repairs, the speed of repairs or replacement or buyback and do whatever is

necessary to bring the product or service up to standard.


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A quality emphasis encompasses entire organization, from supplier to

customer stresses a continuing a commitment by management to have a

continuing, company wide, drive toward excellence in all aspects of

products and services that are important to the customer

Concepts of TQM

a) Continuous Improvement- It is represents continual improvement

of process.b) Employee empowerment- Getting employees involved in product

and process improvement

c) Benchmarking- selecting best practices organization to use as a

standard for performance


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a) Prevention costsIt is related to expenditure before breakdown occurs to reduce the potentialfor defects. For example is maintenance costs.

b) Appraisal CostsIt is related to expenditure assessing auditing the level of quality attained inproduction to evaluating products. For example is inspection costs.

c) Internal failureIt is related to expenditure for correcting or reworking on products or

services due to defects incurred during process. For example reworking cost.

d) External costIt is related to expenditure occur after delivery or production process. Forexample is warranty cost.


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First Stage

ProductDesign or

processdesign

Determine the level of customer involvement by not to focus on thefunctionalities but ease to all user

Second Stage

ManufacturingStage

Inspection used in this stage

1) Inspection of raw materials

2) Production Process

3) Finished Product

Third Stage

After sales

services

The responsibility towards quality after sales services or warranty onproducts sold to customer

There are 3 stages of Quality Control


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It is integral part of quality control and isperformed to detect whether the products

being produced conform to certain standardsor specifications. It involves periodic checkingand measuring before. During and after theproduction process


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1)To maintain certain standards in producing products

2) To meet customer satisfaction

3) To find the problems in the production process

4) To grade the products

5) To find defective products this can be reworked


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Seven Basic Quality Control Tools:

1. Check Sheets

2. Histogram3. Flowcharts

4. Scatter Diagrams

5. Cause-and-Effect Diagram

6. Pareto Analysis

7. Statistical Process Control (SPC)


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It is a tool to identify problems (detect) and

make improvement (eliminate variations) by

using sample statistics


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1. Natural variations

Uncontrollable variations

2. Assignable variationsControllable variations


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1. P = Total Defective

Total No. Observation (N)(n)

2. p = p ( 1p )

n

3. UCL = p + zp

4. LCL = p - zp


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Confidence levels, Z values:

% Z values

95.0 1.96

95.5 2.00

99.0 2.5899.5 2.76

99.7 3.00


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A mobile phone producer has been concerned

about the number of defective mobile phones

found recently. In order to evaluate the truemagnitude of the problem, a production

manager selected 10random samples (N)of

100 units each (n) for inspection. The number

of defective mobile phones found in each

sample is as follows:


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Sample No 1 2 3 4 5 6 7 8 9 10

No ofDefective

3 5 2 7 4 1 3 6 13 6

Step 1, finding the Total no. of defectives

= 3+5+2+7+4+1+3+6+13+6

= 50phones


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Based on the above information, develop a p-chart with z = 3. Is the process under control?

Explain your answer. (10 marks)


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2. P = Total Defective50 = 0.05

(N)(n) 10 (100)

3.p = p 0.05( 1p 0.05) = 0.0218

n 100

4. UCL = p 0.05 + z 3 (p 0.0218) = 0.1154

5. LCL = p 0.05z 3 (p 0.0218) = -0.0154

@ 0


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Sample No. No of Defectives (#) Step 6

Fraction Defective (#/n)

1 3 3/100 = 0.03

2 5 5/100 = 0.05

3 2 2/100 = 0.02

4 7 7/100 = 0.07

5 4 4/100 = 0.04

6 1 1/100 = 0.017 3 3/100 = 0.03

8 6 6/100 = 0.06

9 13 13/100 = 0.13

10 6 6/100 = 0.06


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LCL

0.1154

Fraction Defective

Sample


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Is the process under control? Explain youranswer.

(10 marks)

The process is out-of-cotrol because sampleNo. 9 is above the Upper Control Limit. Aninvestigation should be carried out to find outthe assignable causes.


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Sample of

numberNumber of

detects in Sample1 42 33 34 65 16 97 58 129 4

10 3


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(a) N = 10 ; n = 100 ; z = 3

p = Total Defective / N (n)

= 50 / 10 (100) = 0.05


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UCL = p + p (z)

= 0.05 + 0.0218 (3)

= 0.1154UCL = p - p (z)

= 0.05 - 0.0218 (3)= - 0.0154


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Sample Fraction Defective (F.D)

1 4/100 = 0.04

2 3/100 = 0.03

3 3/100 = 0.034 6/100 = 0.06

5 1/100 = 0.016 9/100 = 0.09

7 5/100 = 0.058 12/100 = 0.129 4/100 = 0.04

10 3/100 = 0.03


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F.D

UCL = 0.1154

p = 0.05

0 1 2 3 4 5 6 7 8 9 10 Sample/LCL

Control (P-Chart)


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F.DUCL = 0.1154

p = 0.05

0 1 2 3 4 5 6 7 8 9 10 Sample/LCL


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(b) Conclusion

The process of making the bolts is outof control since sample no. 8 is

outside the upper control limit. Thus,

the quality control department needs

to investigate the assignable causesthat result in the defect.


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Chicago Supply Company manufacturers paper clips andother office products. Although inexpensive, paper clips haveprovided the firm with a high margin of profitability. Samples

of 200 broken are taken. Results are given for the last 15samples.

Construct a control chart based on 99.7% confidence interval(z=3). Is the process in control?

Sample 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Defectives 4 6 3 4 5 3 5 6 2 7 3 2 14 5 7


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March 2012 Apr 2011(Nil) Oct 2010 (Nil)

Apr 2010 (Nil)

Oct 2009 (A5)

Apr 2009 (Nil)

Oct 2008 (A4)

Apr 2008 (Nil) Oct 2007 (Nil) Apr 2007 (Nil)

Oct 2006 (A5)

CHAPTER 10 - Quality Control

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