Quality is important to organizations and their customers.
Quality is one of the key decisions in operations in today’s highly competitive global market.
Difficult term to define as it can mean different things to different people, so what is meant by Quality?
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www.iso.org
International Organization
for Standardization
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Introduction
Quality is important to organizations and their customers.
Quality is one of the key decisions in operations in today’s highly
competitive global market.
Difficult term to define as it can mean different things to different
people, so what is meant by Quality?
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What is meant by Quality
The International Organization for Standardization (ISO)
defines quality as :“the degree to which a set of inherent
characteristics fulfils requirements” (ISO9000:2000).
Experts definitions:
Edward Deming definition of Quality is “uniformity and
dependability”
Joseph Juran define it in his book (The Quality Gurus ) as
Quality is “fitness for use”
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What is meant by Quality(cont.)
Other definitions
Quality is conformance to standards & requirements.
Quality is the degree to which performance meets
customers expectations.
Quality is The totality of features and characteristics of a
product or service that bears on its ability to satisfy stated
or implied needs. (American Society for Quality)
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What is meant by Quality(cont.)
My Own Definition
Quality means providing the right services in the
right way from the first time and every time for
every customer using highly skilled workforce to
prevent any customer complaints.
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Quality
There are variety of measures to ensure all products and
services meet a high level of quality. Include:
Quality control (QC)
Quality Assurance (QA)
Quality circles
Quality Management
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Quality
Quality Assurance (QA) is a way of preventing mistakes or defects in
manufactured products and avoiding problems when delivering
solutions or services to customers.
Quality Control (QC) is a set of activities for ensuring quality in
products. The activities focus on identifying defects in the actual
products produced.
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.
Quality controlQuality AssuranceTerm
QC is the detection of defects after the event
QA is the prevention of defects before
they happen
Definition
QC focus on identifying defects in the actual
products produced. It is reactive process
QA focus on the process used to make
the product. It is a proactive quality
process.
Focus on
Identify defects after a product is developed
and before it's released
Improve development and test processes
so that defects do not arise when the
product is being developed
Goal
Finding & eliminating sources of quality
problems through tools & equipment so that
customer's requirements are continually met
Establish a good quality management
system and the assessment of its
adequacy
How
Quality Control is usually the responsibility of a
specific team that tests the product for defects
Everyone on the team involved in
developing the product is responsible for
quality assurance
Responsibility
When statistical tools & techniques are applied
to finished products (process outputs), they are
called as Statistical Quality Control (SQC) &
comes under QC
Statistical Tools & Techniques can be
applied in both QA & QC. When they are
applied to processes (process inputs &
operational parameters), they are called
Statistical Process Control (SPC); & it
becomes the part of QA
Statistical Techniques
QC is a corrective toolQA is a managerial toolAs a tool
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Quality Sample types
Sample definition:
Quality: A small part of or a selection from something, intended to show the
quality, style, or nature of the whole;
Marketing: Entities or observations randomly selected to represent the behavior
and characteristics of the entire group
Sample methods:
There are two main types of the sample:
1. Probability Sample
2. Non-probability Sample
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Quality Sample types
Probability Sample:
1. Simple Random
2. Systematic Random
3. Stratified Random
4. Random Cluster
5. Complex Multi-stage Random (various kinds)
Non-probability Sample
1. Convenience
2. Purposive
3. Quota
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Quality Sample types
Simple Random
Each element has an equal probability of selection and each combination of elements
has an equal probability of selection.
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Quality Sample types
Stratified Random
Divide population into groups that differ in important ways (e.g. critical and non-
critical)
This method reduces error compared to simple random.
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Quality Sample types
Random Cluster
Population is divided into groups some of the groups are randomly selected
Cost savings of clustering and the error may smaller if the clusters are similar to
each other.
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Sample Size
To define the sample size you have to know:
Confidence level
It is equal to the accuracy level (95%, 98 %,..).
Confidence interval (form the previous test)
Is the plus-or-minus.
, For example, if you use a confidence interval of 4 and 47% percent of your
sample picks an answer you can be "sure" that if you had asked the question of
the entire relevant population between 43% (47-4) and 51% (47+4) would have
picked that answer
It can be calculate from this formula
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Sample Size
Where
The table below lists some z to LOC values:
the assumed (1st guess) accuracy of the system expressed as a decimalp
number of samples (number of test records used)n
a function of the test's Level of Confidence (LOC)z
ZLOC
99.9%3.3
99.0%2.577
98.5%2.43
97.5%2.243
95.0%1.96
90.0%1.645
85.0%1.439
75.0%1.151
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Sample Size
Below is simple tool use to calculate the sample size (random sample)