1. frequency and times: frequency is the number of times each object appears, and the ratio of the number of times each object appears to the total number is frequency.
2. Frequency distribution table: When using frequency distribution histogram for data analysis, the distribution table is generally listed first, and there are several commonly used formulas: the sum of each group of frequencies is equal to the total number of sampled data; The sum of each group of frequencies is equal to1; Total data × frequency of each group = frequency of the corresponding group.
The purpose of drawing the histogram of frequency distribution is to display the results visually in the frequency distribution table.
3. Histogram of frequency distribution:
(1) When the collected data are taken continuously, we usually group the data appropriately first, and then draw the histogram of frequency distribution.
(2) The general steps of drawing the histogram of frequency distribution: ① Calculate the difference between the value and the minimum value (extreme range) and determine the range of statistics; (2) Determine the number and distance of groups. The more data, the more groups. ③ Determine the demarcation point; ④ Column frequency distribution table; ⑤ Draw the histogram of frequency distribution.
Second, the commonly used statistics:
There are three common statistical charts: bar chart, line chart and fan chart. When solving practical problems, the specific choice of statistical chart depends on the characteristics of statistical chart and the requirements of the problem.
1. Bar chart:
(1) A bar chart represents a certain quantity with a unit length, draws straight bars with different lengths according to this quantity, and then arranges these straight bars in a certain order. Bar charts are divided into bar charts and composite bar charts.
(2) Features: The specific data of each group can be displayed; It is easy to compare the differences between the data; If the data to be represented is independent, bar charts are generally used.
(3) Drawing method: ① In order to make the graphic size suitable, we must first determine the length of the horizontal axis and the vertical axis, and draw the horizontal axis and the vertical axis;
(2) determining the unit length, namely respectively determining the unit length of two axes according to the size and type of data to be represented, and performing equidistant segmentation on the horizontal axis and the vertical axis from zero; (3) Use straight bars with different lengths (or heights) to indicate the specific quantity, and the width of the straight bars should be appropriate, the width of each straight bar should be equal, and the distance between the straight bars should be equal; (4) To indicate the statistical object, unit and quantity represented by each straight bar chart, write down the name and drawing date of the statistical chart, and have a legend for the composite bar chart.
2. Broken line statistical chart:
(1) A broken-line statistical chart represents a number with unit length, draws points according to the number, and then connects these points with line segments in turn, indicating the increase or decrease of statistics with the rise or fall of broken lines.
(2) Features: The broken-line statistical chart can clearly show the increase or decrease of data. If the data represented is to understand the changes with time, then use the broken line statistical chart.
(3) Drawing method: ① Collating data according to statistical data; (2) Representing a certain quantity with a certain unit and drawing the vertical and horizontal axes; (3) According to the numbers, draw each point at an appropriate position on the vertical and horizontal axes; ④ Connect points with line segments in turn;
⑤ Whether the data in the statistical chart is compiled by statistical data.
3. Fan chart:
(1) The pie chart represents the whole with circles. Each sector in the circle represents a different part of the whole, and the size of the sector reflects the percentage of this part in the whole. Such a chart is called a fan chart.
(2) Features: In the sector statistical chart, the percentage of each part in the total is equal to the degree of the sector central angle corresponding to 360? The proportion of. If you want to know the percentage of each data, you will generally use a fan-shaped statistical chart.
(3) Drawing method: ① First, calculate the percentage of each part in the total.
② Then calculate the degree of the fan-shaped central angle representing the number of parts.
(3) Draw a circle with an appropriate radius, and draw each sector on the circle according to the degree of the central angle calculated above.
(4) In each sector, indicate the number name and percentage of each part and distinguish them with different colors.
⑤ Write your name and drawing date.
Third, the advantages of various statistical charts:
Bar chart: the specific figures of each item can be clearly displayed; Broken line statistical chart: can clearly reflect the changes of things; Department statistical chart: it can clearly show the percentage of each part in the total.
Common inspection methods
(1) column frequency distribution table, and draw frequency distribution histogram;
(2) Obtaining information from statistical charts to complete the problem of topic design;
(3) Complete the histogram and statistical chart of frequency distribution, and answer questions;
(4) Drawing and conversion of statistical charts.
Misunderstanding reminder
(1) When doing statistics, there is no reasonable choice of statistical charts;
(2) When extracting the information in the chart, it is incomplete and has omissions;
(3) The number of parts misjudged when drawing the sector statistical chart.