Quality Control and Assurance

1Running title of presentationPR/mo/item IDDate

www.iso.org

International Organization for Standardization


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?


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”


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)


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.


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


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.


.

Quality controlQuality AssuranceTerm

QC is the detection of defects after the eventQA is the prevention of defects before

they happenDefinition

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 developedGoal

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

adequacyHow

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 assuranceResponsibility

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


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



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



Simple Random

Each element has an equal probability of selection and each combination of elements has an equal probability of selection.



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.



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.


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


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


Sample Size

Below is simple tool use to calculate the sample size (random sample)

Engineering

Quality Control and Assurance