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Indicators used to measure the quality of products
Conference Paper · May 2009
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21-23th May 2009
INDICATORS USED TO MEASURE THE
QUALITY OF PRODUCTS
Lidia Mândru 1, Alina Hârlab 1, Adina Liana Camarda
1
1
”George Bariţiu” University of Brasov, Romania
Corresponding author: Lidia Mândru, [email protected]
Abstract: It is well known that nowadays, clients expect
high quality of purchased products and therefore,
companies have to be able to measure the quality of
products they supply, trying to see the measure in which
those satisfy costumer’s needs and expectations. The
quality level of products can be measured using several
indicators such as partial indicators of quality products,
indicators of quality classes, scraps indicators, indicators
of customer complaints. In the following paper we shall
see how this indicators can be calculated and how they
reflect the quality level of products.
Key words: quality, indicators, measuring the quality of
products
1. INTRODUCTION
The fast evolution of the economic environment
and of the market factors requires increasingly more
that companies should have a flexible production
system, which allows a quick adaptation to the more
and more exigent requirements and needs of the
consumers. The assurance of a high level of product
quality requires among others, to establish the
extent to which the products meet the standards and
rules related to quality, but also the consumers’
requirements and expectations.
As some authors (Fisher, 1998) says, a
comprehensive set of indicators have to measure
quality from several perspectives and at different
points in order to provide information about: quality
of the finished product, lack of quality of the
finished product and quality of the process (how
reliably does it produce quality products?).
Data obtained by means of indicators that
measure quality shall be thoroughly analyzed and
on this basis, the management will establish the
measures to be taken to improve quality. Late
implementation of these measures will generate
losses in chain, whose coverage will require
additional efforts made by the organization.
As future research direction we shall aplly the
indicators described bellow on several products
trying to find the best system to measure the quality
of products.
2. GENERAL INFORMATION
2.1 What does quality and product terms mean?
What is a quality indicator?
According to ISO 9000:2000 (EN ISO 9000,
2000), quality represents „the extent to which a set of
inherent1 characteristics satisfies the requirements".
Philip B. Crosby defines quality as the
”conformance to requirements” while for Joseph M.
Juran2 quality represents the ”fitness for use”.
From another point of view (Ciobotaru et al.,
2001), quality is an amount of features with a dynamic
evolution induced by the technical progress, which
involves the design and development of new products
with superior features and performances.
The same standard (EN ISO 9000, 2000) defines
the product as „the result of a process”, stating that
there are four generic categories of products namely:
hardware (e.g.: the mechanical part of an engine),
processed materials (e.g.: lubricants), software (e.g.: a
computer programme) and services (e.g.: transport).
Quality indicators represent the numeric
expressions of the quantitative side of the analysed
phenomenon, expressing its level, structure and
dynamics (Pruteanu et al., 2000).
To be efficient, an indicator should have the
following characteristics (Morariu, 2006): it must be
1
The term "inherent" refers to the presence in something of a permanent feature (EN ISO 9000, 2000).
2
Joseph Moses Juran: American professor of Romanian origin (he was born in 1904, in Braila, Romania)..
”smart” (simple, measurable, accepted, realistic,
temporarily).
Kc
i
ocn
i
a) partial indicators of quality products
b) indicators of quality classes
c) scraps indicators
d) indicators of customer complaints.
a) Partial indicators of quality products reflect a
series of measurable characteristics of products,
their content referring to a trait, characteristic or
property that meets certain requirements.
For expressing these indicators there are used
measuring units according the parameters taken into
account (e.g.: for expressing the quality of engines
there are used as indicators weight/horse power, the
compression ratio, fuel consumption, maximum
power, etc.).
Product quality assessment is realized by
comparing the results obtained on the basis of
concrete measurement of product characteristics, with
limits/levels specified in standards, internal notes,
specifications or other normative documents.
b) Indicators of quality classes
This kind of indicators is used when products can
be placed on quality classes according to their quality
characteristics.
The indicators of quality classes are divided into two
categories:
1.
Indicators used for companies that realize a
homogeneous production
2.
Indicators used for companies that realize a
heterogeneous production
1. Indicators used for companies that realize a
homogeneous production
In this case, the assessment of quality of the products
that can be grouped into classes is realized using the
following indicators:
• The medium coefficient of quality
• The medium selling price of the product
•
The medium coefficient of quality is
calculated as follows:
(1)
qi
3. INDICATORS USED TO MEASURE THE
QUALITY OF PRODUCTS
Regarding the measure of quality, we can use a
system of indicators among whom the most important
are the following (Plumb & Ratiu-Suciu, 2003; Olaru,
1999):
qi
i o
where, i – the number of quality classes
c – the cipher that correspond to
„i”
quality class; c = 0, 1, 2 ... i
q
–
the
physical
production
that corresponds to „i” quality class.
The share of „i” quality production in total production
is calculated using the following formula:
q
q*i n i
(2)
qi
i o
It results that the indicator can be also calculated
using the relationship:
Kc
n
ci qi*
(3)
i o
The closer to zero the medium coefficient of quality
is, the higher is the quality of product.
The medium selling price of the product can be
determined as follows:
n
p
i 1
qi
pi
(4)
n
qi
i 1
where, p – the price corresponding to „i” quality class.
This indicator is used when, from the same raw
materials are manufactured products of different
quality classes, each class of quality having different
prices.
The more the medium price is closer to that of the
high quality products the better shall be the quality of
products because the extra quality or first quality
production is larger.
2. Indicators used for companies that realize a
heterogeneous production
n
In this case, the appreciation of the quality of
products that can be grouped into quality classes is
realized using several indicators (the generalized
medium coefficient, costs at 100 EUR turnover due
to inadequate quality, etc.).
The generalized medium coefficient can be
calculated using the following formula:
n
KG
pi
qi
1 Kn i
i
qi pi i
(5)
1
where, i – the type of the manufactured
product
K i - the medium coefficient
of quality
q – the physical volume of
production
p – the price.
The generalized medium coefficient can be also
determined taking into account the share that a certain
type of product held in the total production:
i
Pi
nq
These indicators are related to the expression of
nonquality within the company and they are based on
production sharing in the good and scrap production.
According to Merriam-Webster's Collegiate
Dictionary, Eleventh Edition (Merriam-Webster,
2003) scrap is defined as:
„…4 b: manufactured articles or parts rejected or
discarded and useful only as material for
reprocessing”. Scraps can be:
recoverable: deficiencies can be remedied by
additional processing;
unrecoverable: deficiencies can not be solved.
Indicators for scraps assessment are:
• the value of scrap production;
• the percentage of scrap production;
• the company’s loss value because of scrap
production;
• the percentage of loss because of scrap
production.
•
The value of scrap production can be
calculated as follows:
pi
n
(6)
q
i
qrdi crdi
Rv =
pi
n
qrri crri
i 1
(9)
i 1
i 1
n
and
KG
Ki Pi
(7)
i 1
The closer to value that indicates the superior
quality class is the indicator value the higher gets the
quality level of products.
where, i – the type of product qrd – the quantity of
unrecoverable scraps crd – the unit cost of an
unrecoverable scrap qrr – the quantity of
recoverable scraps crr – the unit cost of retrieving
a recoverable scrap . The percentage of scrap
production The calculating formula is:
Ppr =
Expenditures at 100 EUR turnover due to
inadequate quality (ChCA100)
RV 100
(10)
n
qi ci
i 1
This indicator is determined as specified below:
where, Rv – the value of scrap production
n
ChCA100
Cpn
100
(8)
CA
where, Cpn – expenditure on
improper production
CA – turnover.
These expenses include: costs of labor and
materials used to manufacture improper quality
production, the differences resulting from declassified
production, additional costs spent with expertise and
retrievals, etc.
c) Scraps indicators
qi ci - the value of production expressed
i 1
in costs
•
The loss value because of scrap production
can be determined as follows:
Pr = Rv - Srec
where,
Rv – the value of scrap production
(11)
Srec – the amounts recovered by company through the
scraps capitalization, the amounts withheld from
people in guilt and compensations received from
suppliers who have delivered defective materials that
have generated these scraps.
•
The percentage of loss because of scrap
production can be calculated using the following
formula:
Pr
Pr % =
100
(12)
n
qi ci
i 1
where, Pr – company’s loss value because of
production
scrap
n
i 1
in costs.
Scraps indicators may be included in the ”balance of
quality costs” as elements of the analysis of the
company’s nonquality.
d) Indicators of customer complaints These
indicators reflect the nonquality and they refer to:
a)
the quantity of products refused upon arrival or
claimed during the warranty period and the value of
those products;
b)
the weight of the quantity and value of
rejected or claimed products in the total production;
c)
the costs of retrieving the refused or claimed
products;
d)
the number of repair requests at 1.000
delivered pieces.
Within the analysis of complaints, there can be
obtained useful information regarding the nature and
frequency of defects, the behavior of products while
exploiting them, the customers satisfaction, etc. and
qi ci - the value of production expressed
there can be taken measures to eliminate the deficiencies of
production activity.
4. CONCLUSIONS
Applying the indicators that express quality,
companies can measure the qualitative level of their
products, taking afterwards the necessary measures to
improve their quality:
- identification of defects / deficiencies that have
caused
the
decrease
of
product
quality removal
of
software
defects,
changes
in
manufacturing technology, design corrections, etc. controlling, monitoring and analysis of the
effectiveness for the applied corrective actions, in
order to determine whether they generate the expected
results.
Therefore,
when it
comes about
quality measurement, it has to be said that
measurement is not the goal, improving quality is the
goal.
Lack of a system for measuring the quality makes
it impossible to coordinate and orient processes in
order to meet customer requirements; it is very
important to know the real quality level of a product so
that it can be then compared with the target value.
References
1. Ciobotaru, V.; Angelescu, A. & Visan, A. (2001).
Technical
Progress,
Quality,
Standardization. Academy of Economic Studies
Publishing House, pp. 54-58, ISBN 973-5940-36-1,
Bucharest
2. Fisher, L. H. (1998). Can’t Someone Tell Me How to
Measure Quality? Proceedings of the 45th Society for
Technical Communication Conference, Anaheim,
California, 17-20 May 1998, Session MG 2L.
Available
from:
http://www.stc.org/confproceed/1998/PDFs/00028.P
DF, Accessed at 10/03/2009
3. International Standard Organization (2000). EN ISO
9000: 2000. Quality Management Systems.
Fundamentals and Vocabulary, pp.15, 20
4. Merriam - Webster's Collegiate Dictionary,
Eleventh
Edition (2003). Springfield, USA,
ISBN(10):
0877798095,
ISBN(13):
9
780877798095,
Available
from
http://www.merriamwebster.com/dictionary/scrap,
Accessed: 05/02/2009 5. Morariu, C.O. (2006). The
Quality Management System. Transilvania University
Publishing House, pp. 93-98, ISBN 978-973-635-7381, Brasov 6. Olaru, M. (1999). Quality Management.
Economic Publishing House, pp. 227-253 ISBN 973590-158-7, Bucharest
7.
Plumb, I. & Ratiu-Suciu, I. (2003). Industrial
Economics. Economic Tribune Publishing House, pp.
175-192, ISBN 973-825-761-1, Bucharest
8.
Pruteanu, O. et al. (2000). Quality Management
and Control. Tehnica Info Publishing House, pp. 176209, ISBN 9975-910-91-2, Chişinău
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