Statistical methods of data analysis are described in sufficient detail in the domestic literature. In the practice of Russian enterprises, meanwhile, only some of them are used. Let's consider some methods of statistical processing.
General information
In the practice of domestic enterprises, mainly statistical methods of control are common. If we talk about the regulation of the technological process, then it is noted extremely rarely. The application of statistical methods provides that the enterprise forms a group of specialists who have the appropriate qualifications.
Meaning
According to ISO ser. 9000, the supplier needs to determine the need for statistical methods that are applied in the process of developing, regulating and verifying the capabilities of the production process and the characteristics of products. The methods used are based on the theory of probability and mathematical calculations. Statistical data analysis methods can be implemented at any stage of the product life cycle. They provide an assessment and account of the degreeproduct heterogeneity or variability of its properties relative to the established nominal values or required values, as well as the variability of the process of its creation. Statistical methods are techniques by which it is possible to judge the state of the phenomena that are being studied with a given accuracy and reliability. They allow you to predict certain problems, develop optimal solutions based on the studied factual information, trends and patterns.
Use directions
The main areas in which statistical methods are widely used are:
- Process control.
- Product acceptance. It uses statistical quality methods.
- Study of stability and accuracy of technological operations.
- Reliability calculation and testing.
Developed country practice
Statistical methods are the basis for creating products with high consumer characteristics. These techniques are widely used in industrialized countries. Statistical methods are, in fact, guarantees that consumers receive products that meet established requirements. The effect of their use has been proven by the practice of industrial enterprises in Japan. It was they who contributed to the achievement of the highest production level in this country. Long-term experience of foreign countries shows how effective these techniques are. In particular, it is known that Hewlelt Packard, using statisticalmethods, was able to reduce the number of marriages per month from 9,000 to 45 units in one of the cases
Difficulties in implementation
In domestic practice, there are a number of obstacles that do not allow the use of statistical methods for studying indicators. Difficulties arise due to:
- The lack of an adequate understanding of the essence and significance of techniques, the importance of understanding, transforming and using information among most specialists and business leaders.
- Ignorance of both the statistical methods themselves and the order of their application.
- The majority of specialists lack experience in processing empirical information.
- Distrust in the reliability of the results.
- Lack of clear, easy-to-read manuals without involving the mathematical apparatus of benefits.
Program development
It must be said that determining the need for certain statistical methods in the field of quality, choosing, mastering specific techniques is a rather difficult and lengthy job for any domestic enterprise. For its effective implementation, it is advisable to develop a special long-term program. It should provide for the formation of a service whose tasks will include the organization and methodological guidance of the application of statistical methods. Within the framework of the program, it is necessary to provide for equipping with appropriate technical means, training of specialists, determining the composition of production tasks thatshould be solved using the chosen methods. Mastering is recommended to start with using the simplest approaches. For example, you can use the well-known elementary statistical methods of production management. Subsequently, it is advisable to move on to other methods. For example, it can be analysis of variance, selective processing of information, regulation of processes, planning of factorial research and experiments, etc.
Classification
The statistical methods of economic analysis include different techniques. Needless to say, there are quite a few of them. However, a leading expert in the field of quality management in Japan, K. Ishikawa, recommends using seven basic methods:
- Pareto charts.
- Group information by common features.
- Control cards.
- Cause and effect diagrams.
- Histograms.
- Control sheets.
- Scatterplots.
Based on his own experience in the field of management, Ishikawa claims that 95% of all questions and problems in the enterprise can be solved using these seven approaches.
Pareto chart
This statistical data method is based on a certain ratio. It has been called the "Pareto Principle". According to him, out of 20% of the causes, 80% of the consequences appear. The Pareto chart in a visual and understandable form shows the relative influence of each circumstance on the overall problem in descending order. This effect can be studied in terms oflosses, defects caused by each cause. Relative impact is illustrated with bars, cumulative impact of factors with a cumulative straight line.
Cause and effect diagram
On it, the problem under study is conditionally depicted in the form of a horizontal straight arrow, and the conditions and factors that indirectly or directly affect it are in the form of oblique arrows. When building, even seemingly insignificant circumstances should be taken into account. This is due to the fact that in practice there are quite often cases in which the solution of the problem is ensured by the exclusion of several seemingly insignificant factors. The reasons that influence the main circumstances (of the first and subsequent orders) are depicted on the diagram by horizontal short arrows. The detailed diagram will be in the form of a fish skeleton.
Group information
This economic-statistical method is used to streamline the set of indicators that were obtained by evaluating and measuring one or more parameters of an object. As a rule, such information is presented in the form of an unordered sequence of values. These can be the linear dimensions of the workpiece, the melting point, the hardness of the material, the number of defects, and so on. Based on such a system, it is difficult to draw conclusions about the properties of the product or the processes of its creation. Ordering is carried out using line graphs. They visually show changes in observed parameters over a certain period.
Control sheet
As a rule, it is presented in the form of a frequency distribution table for the occurrence of the measured values of the object's parameters in the corresponding intervals. Checklists are compiled depending on the purpose of the study. The range of indicator values is divided into equal intervals. Their number is usually chosen equal to the square root of the number of measurements taken. The form should be simple in order to eliminate problems when filling out, reading, checking.
Histogram
It is presented in the form of a stepped polygon. It clearly illustrates the distribution of measurement indicators. The range of set values is divided into equal intervals, which are plotted along the x-axis. A rectangle is built for each interval. Its height is equal to the frequency of occurrence of the value in the given interval.
Scatterplots
They are used when testing a hypothesis about the relationship of two variables. The model is built as follows. The value of one parameter is plotted on the abscissa axis, and the value of another indicator is plotted on the ordinate. As a result, a dot appears on the graph. These actions are repeated for all values of the variables. If there is a relationship, the correlation field is extended, and the direction will not coincide with the direction of the y-axis. If there is no constraint, it will be parallel to one of the axes or will be circular.
Control cards
They are used in process evaluation for a specific period. The formation of control charts is basedon the following positions:
- All processes deviate from set parameters over time.
- The unstable course of phenomena do not change by chance. Deviations that go beyond the boundaries of the expected limits are non-random.
- Some changes can be predicted.
- A stable process can occasionally deviate within the expected limits.
Use in the practice of Russian enterprises
It should be said that domestic and foreign experience shows that the most effective statistical method for assessing the stability and accuracy of equipment and technological processes is the compilation of control charts. This method is also used in the regulation of production operations, the study of the potential of production capacities. When constructing maps, it is necessary to choose the parameter under study correctly. It is recommended to give preference to those indicators that are directly related to the intended use of the product, that can be easily measured and that can be influenced by process control. If such a choice is difficult or not justified, it is possible to evaluate the values correlated (interrelated) with the controlled parameter.
Nuances
If it is not economically or technically possible to measure indicators with the accuracy required for mapping according to a quantitative criterion, an alternative sign is used. Terms such as "marriage" and "defect" are associated with it. The latter is understood as each separate non-conformity of the productestablished requirements. Marriage is called products, the provision of which is not allowed to consumers, due to the presence of defects in it.
Features
Each type of card has its own specifics. It must be taken into account when choosing them for a particular case. Cards by quantitative criterion are considered more sensitive to process changes than those that use an alternative feature. However, the former are more labor intensive. They are used for:
- Debug process.
- Assessing the possibilities of technology implementation.
- Checking the accuracy of the equipment.
- Tolerance definitions.
- Multiple valid ways to create a product.
Extra
If the disorder of the process is characterized by a shift in the average value of the controlled parameter, it is necessary to use X-maps. If there is an increase in the dispersion of values, R or S models should be chosen. It is necessary, however, to take into account a number of features. In particular, the use of S-charts will make it possible to more accurately and quickly establish the disorder of the process than R-models with the same sample sizes. At the same time, the construction of the latter does not require complex calculations.
Conclusion
Quantitative methods of analysis in economics allow us to explore the factors that are found in the course of a qualitative assessment, in space and dynamics. They can be used to perform predictive calculations. Statistical methods of economic analysis are notinclude methods for assessing the cause-and-effect relationships of economic processes and events, identifying promising and untapped reserves for improving performance. In other words, factorial techniques are not included in the considered approaches.
