Preliminary Sample of a Serial Number Table. Table Name (General Title)

The purpose of the research requires analysis. Therefore, in this case, it is necessary to combine groups to obtain a number of appropriate groups. The basic principle of grouping is based on the law of motion of research in philosophy, which is "quantity of variation leads to quality of variation". It is necessary to deeply analyze the scientific theory combined with a full analysis of existing reality and consider the purpose and requirements of the proposed research to determine the amount of variation accumulated to a certain level, which will create a new quality and must be formed into another group. On the basis of such analysis, the number of groups needed to divide will be determined. For example, dividing the population according to working age, 3 groups are formed: groups of residents under working age, groups of residents in working age, and groups of residents beyond working age. Grouping the population according to school age, forming a number of necessary groups to meet the purpose of building a strategic plan for the development of the education and training sector to meet the learning needs of the population: preschool groups (nursery groups, kindergarten groups), primary school groups, secondary school groups, and university groups.

b. Determine the nest distance

Only applicable to group-interval grouping. Each group has a range of variables. Each range of variables has 2 limits: lower limit and upper limit. These are also 2 limits of 1 group. The lower limit of the group is the smallest variable of the group. The upper limit of the group is the largest variable of the group. Grouping with 2 limits of the range of variables belonging to the research criterion is called group-interval grouping.

The nest distance is the difference between the upper limit and the lower limit of the nest: Nest distance = Upper limit – Lower limit

There are 2 types of group spacing: Equal group spacing and unequal group spacing. On this basis, groups with equal group spacing and groups with unequal group spacing are formed.

Specific method applied to determine group distance: Depending on the type of grouping with equal or unequal group distance, apply the appropriate method to determine group distance.

- In case of grouping with unequal group distance: The overall units have many differences in quality and the quantitative changes are not uniform. Therefore, determining the group distance is based on the method of deeply analyzing the actual existence of the research phenomenon to consider the degree of variation in the number of variables, the overall units of the research phenomenon will have the same or nearly the same basic properties and characteristics, from which they will be classified into the same group. If this limit of variable quantity is exceeded, another group will be formed. The range of variable quantity that forms a group is the group distance.

- In case of grouping with equal group distance: The overall units of the research phenomenon do not have big differences in quality and basic characteristics, in other words, there is qualitative homogeneity; the quantitative changes in the overall units are generally

takes place quite evenly, without much difference. Therefore, the method of determining the distance between groups is carried out according to the formula:

d = (2.1)

In which: d: Distance between groups

x max : Maximum variable of the grouping criterion x min : Minimum variable of the grouping criterion n: Number of groups to be divided

Example 2.1: Determine the group distance of the sales grouping criterion of the trade industry in the research year with the data: the largest variable in sales is 550 billion VND and the smallest variable in sales is 310 billion VND. The number of groups planned to be divided is 8 groups. The grouping requirement is to have equal group distance and the limit of the previous group coincides with the limit of the next group:

Determine nest spacing:

d = = = 30 billion dong

Divide into 8 groups as required:

Arrange the 8-group variable quantity distribution array according to sales:

Table 2.1. Forming 8 teams according to sales

Organization order

Sales (variable quantity: x i ), (unit: billion VND)
1	310 – 340
2	340 – 370
3	370 – 400
4	400 – 430
5	430 – 460
6	460 – 490
7	490 – 520
8	520 – 550

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Note: In case the grouping does not have a lower limit for the first group and an upper limit for the last group, to calculate the middle value of these two groups, it is necessary to assume their missing limit values. The method of calculating the assumed missing limit values of the groups is to assume that the distance between their groups is equal to the distance between the groups adjacent to them. Take the existing limit of the group and add or subtract the assumed group distance.

2.2.5. Forms of statistical synthesis

2.2.5.1. Level-wise synthesis and centralized synthesis

- Synthesis at each level is the organization that synthesizes investigation documents step by step, from lower to higher levels according to a pre-planned plan. The agency in charge of synthesizing at each level

Synthesize documents within the assigned scope and then send the results to a higher level to synthesize on a broader scale. In this order, the documents are finally sent to the central level, where the final synthesis will be conducted, calculating general indicators that reveal the situation of the entire research phenomenon. Synthesis at each level is often applied in periodic statistical reports and some specialized surveys. The data is synthesized by each level, each level generally understands the situation of its locality or unit, and can self-check to detect errors in the survey documents. On the other hand, the synthesis at each level is relatively concise, promptly serving the information requirements of each level. However, the scope of synthesis at each level is often small, and the synthesis results often only include a certain number of indicators.

- Centralized synthesis is when all the investigation documents are gathered in one place to conduct the synthesis from beginning to end. In centralized synthesis, people often have to use modern means to quickly and accurately calculate complex indicators. Therefore, centralized synthesis reduces a lot of manual work. However, providing synthesis results to serve subordinates is often not fast.

In practice, one can combine the two forms of synthesis together. Based on the research requirements of the levels, the central synthesis agency assigns the levels to synthesize a number of indicators to meet the immediate research requirements. Then send the results and all documents to the central synthesis agency for synthesis according to the established plan.

2.2.5.2. Manual synthesis and machine synthesis

- Manual synthesis is a simple form of synthesis using manual tools such as paper, pens, rulers, etc. In this synthesis method, people use their hands, eyes, etc. to count and allocate each expression of the synthesized criteria. On that basis, a summary table is created showing the synthesized results. Thus, manual synthesis is performed similarly to counting votes in an election. Manual synthesis is simple and easy to perform, but it is very time-consuming and does not meet different research requirements. Whenever it is necessary to change the grouping criteria or group distance, people often have to re-organize the synthesis. With the strong development of information technology, this synthesis method seems to be no longer used.

- Machine synthesis is a form of synthesis using electronic computers. In this form, we must first build a data entry software program and then enter the data into the computer. With the use of scanners as it is today, entering data into the computer not only saves time but also ensures high accuracy. Machine synthesis not only improves accuracy, shortens time, but can also meet all different requirements in synthesis. Therefore, in current surveys, people often use this form of synthesis.

2.2.6. Presentation of statistical data

After synthesizing statistical survey documents, in order to promote its effect on the statistical analysis stage, it is necessary to present the synthesis results in a form that is most convenient for later use. Normally, people present the synthesis results using statistical tables, statistical graphs...

2.2.6.1. Statistical table

A statistical table is the most common form designed with a number of columns and rows to present statistical summary results expressed in specific numbers:

The structure of a statistical table includes form and content:

- Form of statistical table: Table number, table name, titles: variable quantity (x i ), frequency (f i ) or frequency (f i '), cumulative frequency (S Me ). Vertical columns and horizontal rows to present data, reflecting the scale of the research phenomenon. Columns and rows all have titles reflecting the name of the indicator, reflecting the research content of the columns and rows of the statistical table. The statistical table can have columns, rows of totals by group, group and total overall research use, with rows recording column order for easy tracking.

- Content of the statistical table: consists of 2 main parts, the topic part and the explanation part. The topic part for a simple table is to present the variables of the grouping criteria or to present the manifestations of the attribute criteria. For a combined table, it is to present the names of the subject or parts of the subject, sometimes also the system of indicators, manifestations of the research attribute criteria. The explanation part presents the frequency, frequency, explanatory indicators or cumulative frequency... in accordance with the purpose, requirements, and analysis proposed for the research object.

Based on the way the table is structured, there are different types of tables: simple tables, disaggregated tables, and combined tables. Simple tables have few columns and rows, and simple content, such as the table topic is a quantitative criterion or an attribute criterion; the table explanation includes frequency or frequency and cumulative frequency. Combined tables are large-scale tables, with a presentation topic that combines many quantitative and attribute criteria; many research indicators; the explanation combines many criteria such as frequency, frequency, cumulative frequency, and explanatory indicators, etc.

When applying the construction of statistical tables, the principle should be thoroughly understood: the scale of the table should not be too large, and too many indicators and classification criteria should not be combined. Because it will be very difficult to perceive, compare indicators, analyze and comment on the research phenomenon.

Table 2.2. Preliminary sample of a statistical table Serial number. Statistical table name (general title)

Explanation

Topic section

- Frequency, frequency, cumulative frequency - Indicators according to analysis requirements
(a)	(b)	...	(1)	(2)	(3)	...	(…)	Add
- Grouping criteria: + Variable quantity + Properties - Indicator name - Overall, parts - …
Add

2.2.6.2. Statistical graph

Statistical graphs are drawings or geometric lines used to conventionally describe synthesized and calculated statistical data. The graphs represent the general characteristics and nature of the development process and development trends of the research phenomenon. The synthesized data described on the graphs help viewers perceive in a specific, clear and convincing way the trends and laws of development and fluctuations of the research phenomenon, and at the same time see the level of development of the units in the whole, the high and low level of development of the research phenomenon over time. Statistical graphs are designed and presented in many different shapes: circles, blocks, zigzag lines and with many outstanding and beautiful colors to attract viewers...

Frequency 12

capacity 10

Figure 2.1. Example of statistical graph

CHAPTER SUMMARY

Statistical investigation is the collection of documents on economic and social phenomena and processes in a scientific manner and according to a unified plan.

Statistical surveys need to ensure the basic requirements of a statistical activity in general: honesty, accuracy, completeness and timeliness.

Based on the continuity and systematicity of the surveys, statistical surveys can be divided into two types: Regular surveys and irregular surveys. Regular surveys collect data from individuals in the population continuously, closely following the process of emergence and development of the research phenomenon. Irregular surveys collect data from individuals in the population intermittently, not linked to the process of emergence and development of the phenomenon.

Depending on the scope and purpose of the investigation, whether it reflects the whole or a part of the whole, the investigation can be classified into complete investigation and incomplete investigation. Complete investigation is to collect documents about all individuals of the whole, without omitting any individual. Partial investigation is to collect documents about a number of individuals selected from the whole.

To organize an investigation well requires the development of a detailed, meticulous, specific and comprehensive investigation plan. An investigation plan is a document that clearly defines the issues that need to be resolved and understood throughout the investigation process. It acts as a plan to guide the investigation. The content of the investigation plan always changes to suit each investigation. But in general, each investigation plan has the following basic issues:

- Determine the purpose of the investigation

- Identify the investigation subject and investigation unit

- Determine the content of the investigation

- Determine the observation method

- Regulations on time and period of investigation

- Design survey form and explanation of how to fill out survey form

The requirement of statistical investigation is to ensure accuracy with a high level of reliability. However, in practice, the investigation to ensure this requirement is not simple due to the phenomenon of statistical error. Error in investigation is the difference between the values of the investigation criteria on individuals and its actual value. Error affects the quality of the investigation and the quality of the results of data synthesis and analysis. To minimize error, it is necessary to find out the cause of error.

Statistical grouping is based on one (or several) criteria, dividing the units of the research phenomenon into groups of different characteristics.

Statistical analysis is one of the important methods of statistical synthesis, and is also the basis for applying other statistical analysis methods. This is one of the methods commonly used in statistical research, it can be used in all 3 stages: investigation, synthesis and analysis.

To perform statistical analysis, it is necessary to master the following main contents:

- Concept

- Types of clustering and selection of statistical clustering criteria

- Steps of statistical clustering process

- Determine the nest number

- Distribution series. When presenting statistical data, it can be represented by statistical tables and statistical graphs.

Statistical tables are a form of presenting statistical documents in a systematic, reasonable and clear way, aiming to highlight the quantitative characteristics of the research phenomenon.

Statistical graphs and charts are geometric drawings or lines used to conventionally describe statistical documents. Statistical graphs and charts use numbers combined with lines and colors to present and analyze quantitative characteristics of phenomena. Therefore, viewers do not have to spend much time reading numbers but still perceive the main problem easily and quickly.

REVIEW QUESTIONS

1. What is statistical investigation? Analyze the basic requirements of statistical investigation.

2. Distinguish between types of statistical surveys. Give illustrative examples.

3. Present the main contents of a statistical investigation plan.

4. Use the question types to create a simple survey for a survey related to your expertise.

5. Describe the types of errors in statistical surveys. Causes of errors in statistical surveys and methods to overcome errors in statistical surveys.

6. Present the concept, meaning and tasks of statistical analysis.

7. Present the concept of grouping criteria and types of grouping criteria. Give examples.

8. Describe the types of statistical disaggregation.

9. Present the concept, effects and forms of presenting statistical data.