4.3.2 Pareto's analysis

Problems of quality are wrapped in losses (the defective products and expenses connected with their production). It is extremely important to explain a picture of distribution of losses. The majority of them will be caused by insignificant number of types of the defects caused by a small amount of the reasons. Thus, to find out the reasons of emergence not numerous it is essential important defects, it is possible to eliminate almost all losses, having concentrated conditions on elimination of these reasons and having postponed consideration of the reasons bringing to other numerous defects so far. The such problem is successfully solved with the help of the chart of Pareto.

In 1897 the Italian economist V. Pareto invented the form showing that the distribution benefits unevenly. The same theory is illustrated on the chart by the American economist M. S. Lorentz in 1907 both scientists proved that in most cases the greatest share of the income or the benefits belongs to a small number of people. Doctor D. M. Dzhuran applied the chart and M. Lorentz's formula in the sphere of quality control to classification of problems of quality on not numerous significantly important and numerous insignificant and called this method Pareto's analysis. He specified that in most cases the overwhelming number of defects and the related losses arises because of rather small number of the reasons.

How to construct Pareto's chart?

Stage 1.

Solve, what problems should be investigated and how to collect data.

1) What like a problem you want to investigate?

Example: defective products, losses in money, accidents.

2) What data should be collected and how to classify them?

Example: by types working, on technological processes.

Note. It is summarized other infrequently meeting signs under the general headings "other".

3) Establish a method and the period of data collection.

Note. If it is recommended, use special forms.

Stage 2.

Develop a control leaf for data recording with the list of types of the collected information. It is necessary to provide a place for graphic data recording of checks in it (table 2.1).

Table 2.1

Control leaf of data recording

Тип дефектов	Группы данных	Итого
Трещины Царапины Пятна Деформация Разрыв Раковины Прочие	     …        …          	10 42 6 104 4 20 14
Итого		200

Stage 3.

Fill a leaf of data recording and count results.

Stage 4.

For creation of the chart of Pareto develop the form of the table for verifications of data, having provided in it columns for results on each checked sign separately, the saved-up sum of number of defects, percent to the general result and the saved-up percent (table 2.2).

Table 2.2

Tables of data for creation of the chart of Pareto

Types of defects	Number of defects	The saved-up sum of number of defects	Percent of number of defects on each sign in total amount	The saved-up percent
Deformation Scratch Sink Crack Spot Gap Other	104 42 20 10 6 4 14	104 146 166 176 182 186 200	52 21 10 5 3 2 7	52 73 83 88 91 93 100
Total	200	-	100	-

Stage 5.

Arrange the data obtained on each checked sign as the importance and fill in the table.

Note. It is necessary to place prochiye group the last line regardless of that, the number as it is made by set of signs turned out how big, the numerical result on each of which is less, than the smallest value received for the sign allocated in a separate line.

Stage 6.

Draw one horizontal and two vertical axes.

1) Vertical axes:

(a) left axis. Apply on this axis a scale with intervals from 0 to the number corresponding to the general result;

(b) right axis. Apply on this axis a scale with intervals from 0 to 100%.

2) Horizontal axis. Divide this axis into intervals according to numbers of controlled signs.

Stage 7.

Construct the stylar chart.

Stage 8.

Draw a cumulative curve (Curve Pareto).

On the verticals corresponding to the right ends of each interval on a horizontal axis put points of the saved-up sums (results and percent) and connect them among themselves pieces of straight lines.

Stage 9.

Apply all designations and inscriptions on the chart:

1) inscriptions the concerning charts (the name, a marking of numerical values on axes, the name of a controlled product, a name of the author of the chart);

2) the inscriptions concerning data (the period of collection of information, object of research and a place of its carrying out, total number of objects of control (figure 2.1)).

Picture-2.3 Diagramma Paretog on types of defects

Digaramma Pareto on result of activity and on the reasons

As already was it is told, creation of the chart of Pareto - a method of definition of not numerous significantly important factors. Distinguish two look such dshchiagramm.

1. Pareto's chart on result of activity.

This chart is intended for identification of the main problem and reflects the following undesirable results of activity:

- quality: defects, breakages, mistakes, refusals, claims, repairs, returns of production;

- prime cost: volume of losses, expense;

- terms of deliveries: shortage of apas, mistakes in billing, failure terms of deliveries;

- safety: accidents, tragic mistakes, accidents.

2. Pareto's chart for the reasons

This chart otraat the reasons proby, arising during production, and is used for a vyyavleiya main of them:

- worker: change, crew, age, experience, qualification, individual characteristics;

- equipment: machines, units, tools, equipment, organization uses, models, shtampyts;

- raw materials: the manufacturer, a type of raw materials, plant - the supplier, party;

- work method: conditions of production, zakuaza - dresses, receptions works, sequence of operations.

Some reasons about Pareto's charts (councils for productive/effective construction)

Councils for creation of charts of Pareto:

1. Use different classifications and make many charts of Pareto. The essence of a problem can be captured, observing the phenomena from the different points of view therefore it is important to test various ways of classification of data, will not come to light important factors not numerous significantly yet, as serves as the purpose of the analysis of Pareto.

2. It is undesirable that the prochiye group factors made big percent. If such occurs, means objects of supervision are classified incorrectly and too many objects in one group. In this case it is necessary to use other principle of classification.

3. If data can be submitted in terms of money, it is best of all to show it on vertical axes of the chart of Pareto. If it is impossible to estimate the existing problem in terms of money, research can be not effective. Expenses - important criterion of measurements in management.

Councils for use of the chart:

1. If are not desirable a factor it is possible to eliminate by means of the simple decision, it should be made immediately irrespective of the fact which insignificant it was. As Pareto's chart is regarded as an effective remedy of the solution of problems, so it is necessary to consider only the important reasons not numerous significantly. However, if relatively the reason is eliminated in the simple way, it will serve an example of an effective solution, and the gained experience, information and moral satisfaction will make big impact on further procedure of the solution of problems.

2. Do not miss opportunity to make Pareto's chart for the reasons.

After identification of a problem by drawing up the chart of Pareto on result, it is important to define the reasons of emergence of a problem to solve it. Therefore if we want improvements, it is important to make Pareto's chart for the reasons.