1. Review the definitions of mean, median and mode.

2. Introduce the example of the textbook P 146R.

Train of thought: The shopping mall counts the sales of each salesperson in a certain month to form a sample, and obtains information from the average, median and mode of the sample data to estimate the overall trend, thus solving the problem.

The difference between (2) and (3) in the example leads to different results. Its purpose is to tell students to flexibly use three kinds of data representatives to solve problems according to the specific requirements of the topic.

This example also objectively reflects the significance of mathematical knowledge in guiding life practice, and also shows the close relationship between statistical knowledge and life practice.

Step 2: Summarize the promotion activities:

Similarities and differences of three data: average, mode and median;

Average, median and mode can all be used as representatives of a set of data, which mainly describe the trend of a set of data. The average value is a widely used quantity.

The average calculation needs all the data and can make full use of all the data information, but it is greatly influenced by the extreme value.

The mode is a quantity that people often care about when a certain data in a group of data appears repeatedly. Mode is not affected by extreme values, which is one of its advantages, and the calculation of median value is rarely affected by extreme values.

The average value is related to each data in a set of data, and the change of any data will cause the corresponding change of the average value.

The median is only related to the arrangement position of the data. The movement of some data has no effect on the median, and it may or may not appear in a given data. When the individual data in a group of data changes greatly, the median can be used to describe its trend.

The average, mode and median obtained in practical problems should be in units.

Step 3: Practice in class:

1. In an environmental knowledge contest, the scores of 50 students in one class are shown in the following table:

The score is 50607080901001010120.

No.2361415541

Find out the mode, median and average of these students' grades respectively.

There are two groups of tourists in the park, A and B, who are playing group games. The ages of the two groups of tourists are as follows: (unit: years old)

Group A: 13, 13, 14, 15, 16, 17, 17.

Group B: 3, 4, 4, 5, 5, 6, 6, 54 and 57.

(1), the average age of group A tourists is, the median is, and the mode is. Among them, the age characteristics of group A tourists can be passed.

(2) The average age of group B tourists is, the median is, and most of them are. Among them, it can better reflect the age characteristics of group B tourists.

Answer: 1. The mode is 90, the median is 85 and the average is 84.6.

2.( 1) 15, 15, 15, mode (2), 5.5,6, median.

Step 4: Practice after class:

1. The monthly salary of 33 employees of a company (RMB) is as follows:

Staff chairman, vice chairman, general manager, manager, administrative staff

No. 1 12 15320

Salary is 5500500035003000250020001500.

(1), find the average, median and mode of the monthly salary of employees in this company?

(2) Assume that the salary of the vice chairman is raised from 5,000 yuan to 20,000 yuan, and the salary of the chairman is raised from 5,500 yuan to 30,000 yuan. What are the new mean, median and mode? (accurate to the nearest yuan)

(3) Which do you think should be used to describe the salary level of employees in this company?

2. A company has 15 employees, and their departments and corresponding employees make the following profits every year.