Page 225 - DMGT524_TOTAL_QUALITY_MANAGEMENT

Total Quality Management

Notes 12. The determination of the control limits, along with the sample size and the sampling
frequency, is one of the most important tasks in …………………… a control chart.
13. A …………………… is the result of some cause that gradually affects the quality
characteristics of the product and causes the point on a control chart to gradually move up
or down from the centre line.

14.5 Design of Experiments and Statistical Process Control

In general usage, design of experiments, or experimental design, (DoE) is the design of any
information-gathering exercises where variation is present, whether under the full control of
the experimenter or not. However, in statistics, these terms are usually used for controlled
experiments. Other types of study and their design are opinion polls and statistical surveys
(which are types of observational study), natural experiments and quasi-experiments (for
example, quasi-experimental design).
In the design of experiments, the experimenter is often interested in the effect of some process or
intervention (the ‘’treatment’’) on some objects (the ‘’experimental units’’), which may be people,
parts of people, groups of people, plants, animals, etc. Design of experiments is thus a discipline
that has very broad application across all the natural and social sciences.
Quality and productivity improvement has become an essential element of the overall strategic
plan for most organizations. This has sparked renewed interest in statistical methods for quality
improvement. Functions for design of experiments (DOE) enable you to create and test practical
plans to gather data for statistical modeling. These plans show how to manipulate data inputs in
tandem to generate information about their effect on data outputs.
Design of experiments (DOE) is a valuable tool:

1. To optimize product and process designs,
2. To accelerate the development cycle,
3. To reduce development costs,
4. To improve the transition of products from research and development to manufacturing,

5. To effectively trouble shoot manufacturing problems.
Today, Design of Experiments is viewed as a quality technology to achieve product excellence at
lowest possible overall cost.

14.5.1 Objectives of Experimentation

The following are some of the objectives of experimentation in an industry:

Improving efficiency or yield
Finding optimum process settings
Locating sources of variability

Correlating process variables with product characteristics
Comparing different processes, machines, materials, etc.
Designing new processes and products.

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