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. Further we consider some methods of statistical processing.
General information
In the practice of domestic enterprises, mainly statistical control methods 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 a group of specialists who have the appropriate qualifications is being formed at the enterprise.
Value
According to the requirements of ISO ser. 9000, the supplier needs to determine the need for statistical methods that are used in the development, regulation and verification of the production process capabilities and product characteristics. The techniques used are based on probability theory and mathematical calculations. Statistical data analysis methods can be implemented at any stage of the product life cycle. They provide an assessment and accounting of the degree of heterogeneity of a product or the variability of its properties with respect to established ratings or required values, as well as the variability of the process of its creation. Statistical methods are techniques by which one can judge with a given accuracy and reliability the state of the phenomena that are being investigated. They allow you to predict certain problems, to develop optimal solutions based on the studied factual information, trends and patterns.
Directions of use
The main areas in which statistical methods are widespread are :
- Process regulation.
- Acceptance of products. In the course of it, statistical methods of quality are used .
- Investigation of the stability and accuracy of technological operations.
- Calculation of reliability and its testing.
The practice of developed countries
Statistical methods are the basis for the creation of products with high consumer characteristics. These techniques are widely used in industrialized countries. Statistical methods are, in fact, the guarantors of consumers getting products that meet established requirements. The effect of their use is proved by the practice of industrial enterprises in Japan. It was they who contributed to the achievement of the highest production level in this country. Many years of experience in foreign countries show how effective these techniques are. In particular, it is known that the company Hewlelt Packard, using statistical methods, was able to reduce in one case the number of defects per month from 9,000 to 45 units.
Implementation difficulties
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 majority of specialists and enterprise managers lack an adequate understanding of the essence and importance of techniques, the importance of understanding, transforming and using information.
- 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 without the use of mathematical apparatus manuals.
Program development
It must be said that determining the need for certain statistical methods in the field of quality, choosing and mastering specific techniques is a rather complicated 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 equipment with appropriate technical means, training specialists, determine the composition of production tasks that should be solved with the help of selected techniques. Mastering is recommended to start with the use of 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 techniques. For example, it can be analysis of variance, selective processing of information, regulation of processes, planning of factor studies and experiments, etc.
Classification
The statistical methods of economic analysis include various techniques. It is worth saying that there are quite a few of them. However, K. Ishikawa, a leading specialist in quality management in Japan, recommends using seven main methods:
- Pareto Charts.
- Grouping information by common features.
- Control cards.
- Causal diagrams.
- Histograms.
- Checklists
- Scatter charts.
Guided by his own experience in the field of management, Ishikawa claims that 95% of all issues and problems at the enterprise can be solved using these seven approaches.
Pareto Chart
This statistical method is based on a specific ratio. It has been called the Pareto Principle. In accordance with it, 80% of the consequences appear from 20% of the causes. The Pareto diagram in a clear and understandable form shows the relative influence of each circumstance on the general problem in a decreasing order. This effect can be investigated on the number of losses, defects provoked by each cause. The relative influence is illustrated by bars, the cumulative effect of factors through the cumulative straight line.
Cause and effect diagram
On it, the studied problem is conventionally depicted in the form of a horizontal straight arrow, and the conditions and factors that indirectly or directly affect it are represented as oblique. When building, even insignificant at first glance circumstances should be taken into account. This is due to the fact that in practice quite often there are cases in which the solution of the problem is ensured by the exclusion of several seemingly insignificant factors. The reasons that affect the main circumstances (first and next orders) are depicted in the diagram by horizontal short arrows. A detailed diagram will take the form of a fish skeleton.
Information grouping
This economic and statistical method is used to streamline the set of indicators that were obtained when 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. This can be the linear dimensions of the workpiece, the melting temperature, 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 done using line graphs. They clearly show changes in the observed parameters over a certain period.
Checklist
As a rule, it is presented in the form of a table of the distribution of frequencies of occurrence of the measured values of the object parameters in the corresponding intervals. Checklists are compiled depending on the goal of the study. The range of values of indicators 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 exclude problems when filling, reading, checking.
bar chart
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 laid off along the abscissa. A rectangle is constructed for each interval. Its height is equal to the frequency of occurrence of the value in a given interval.
Scatter charts
They are used to test the hypothesis about the relationship of two variables. The model is constructed as follows. On the abscissa axis, the value of one parameter is plotted; the ordinate is the value of another parameter. As a result, a dot appears on the chart. These actions are repeated for all variable values. If there is a relationship, the correlation field is elongated, and the direction will not coincide with the direction of the ordinate axis. If the dependence is absent, it is parallel to one of the axes or will have the shape of a circle.
Control cards
They are used in evaluating a process over a specific period. The formation of control cards is based on the following provisions:
- All processes deviate from the set parameters over time.
- The unstable course of the phenomenon does not change by chance. Deviations that go beyond the boundaries of the assumed limits are not accidental.
- Individual changes can be predicted.
- A stable process may accidentally deviate within the assumed boundaries.
Use in 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 potential production capacities. When building maps, you must correctly select the investigated parameter. It is recommended to give preference to those indicators that directly relate to the purpose of the product, can be easily measured and which can be influenced by regulating the process. If such a choice is difficult or not justified, it is possible to estimate the values correlated (interconnected) with the controlled parameter.
Nuances
If it is economically or technically impossible to measure indicators with the accuracy required for mapping according to a quantitative criterion, an alternative feature is used. Associated with such terms as "marriage" and "defect." The latter is understood as each isolated product non-compliance with the established requirements. Defective products are products that are not allowed to be delivered to consumers due to defects in them.
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 criteria are considered more sensitive to process changes than those that use an alternative feature. However, the former are more laborious. They are used for:
- Debugging process.
- Assessment of the possibilities of introducing technology.
- Checking the accuracy of the equipment.
- Definitions of tolerances.
- Mappings of several valid ways to create a product.
Additionally
If the process disorder is characterized by a shift in the average value of the controlled parameter, you must use X-cards. If there is an increase in the scattering of values, one must choose R or S-models. However, it is necessary to take into account a number of features. In particular, the use of S-cards will allow more accurate and faster to establish the process alignment than R-models with the same sample sizes. However, the construction of the latter does not require complex calculations.
Conclusion
Quantitative methods of analysis in the economy allow us to study the factors that are detected during the qualitative assessment, in space and dynamics. With their help, you can perform predictive calculations. Statistical methods of economic analysis do not include methods for assessing the cause-effect relationships of business processes and events, identifying promising and unused reserves to increase performance. In other words, factor approaches are not included in the number of approaches considered.