2. Bar chart-clearly reflects the quantity
3. Broken line statistical chart-it is convenient to display the changing trend of data, and can intuitively reflect this change and the differences between groups.
4. Department chart-reflect the percentage of each part in the total with the size of the department.
5. Steps of frequency distribution-when there are a large number of observations, in order to understand the distribution law of a group of homogeneous observations and facilitate the calculation of indicators, a frequency distribution table can be compiled, which is called frequency table for short.
(1) Find the range: find the maximum and minimum values in the observed values, and the difference is the full range (or extreme range), which is represented by R.
(2) Determination of group segment and group spacing: Determine the number of "groups" according to the sample content, which is generally 8- 15. When there are fewer observation units, the number of groups may be relatively small, while when there are more observation units, the number of groups may be relatively large. The group spacing is rounded by the total distance of110, which is convenient for summary calculation. The first group should include the minimum values of all observed values, and the last group should include the maximum values of all observed values, and write down their lower and upper limits. The starting point and the ending point of each segment are called the lower limit and the upper limit respectively. A segment contains the lower limit but not the upper limit, and its median value in the group is (lower limit+upper limit) /2 of the segment. The difference between the lower limits of two adjacent groups of line segments is called group distance.
(3) List marking: determine the group boundaries and list them in the form of Table 2. 1, and summarize the original data by computer or marking method to get the number of observation cases in each group, that is, the frequency. Columns (1) and (3) in the table are required frequency tables.
6. The high frequency of the corresponding group