"Statistical Survey" data collection, organization and description PPT courseware (sampling survey in the second lesson)

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"Statistical Survey" Data Collection, Arrangement and Description PPT Courseware (Sampling Survey in Lesson 2)

Part I: New Knowledge Analysis

Question 2: There are 2,000 students in a school. If you want to know the students’ love for TV programs in five categories: news, sports, animation, entertainment, and opera, how to conduct a survey?

You can use a comprehensive survey method to investigate all the students in the school one by one, and then organize the collected data to calculate the students' love for five categories of TV programs.

However, due to the large number of students, a comprehensive survey takes a long time and consumes a lot of manpower and material resources. Therefore, it is necessary to find a way to understand the preferences of students in the school for various TV programs without conducting a comprehensive survey, so as to save time and effort. And it can solve the problem. This is the sample survey we are going to discuss.

Sampling survey is a method that only selects a part of the subjects for survey, and then infers the situation of all subjects based on the survey data. In question 2, we only select a part of the students for survey, and then analyze the characteristics of the surveyed students. Use data to infer the popularity of TV programs among students across the school.

All students in the school are the entire object to be inspected and are called the population.

Each student who makes up the population is called an individual.

The portion of students selected for the survey constitutes a sample of the population.

So, how many students should be selected for the survey?

How to select the students under investigation?

If only a few students are selected for investigation, the sample will not be representative and cannot objectively reflect the overall situation; if a large number of students are selected for investigation, although the sample will be representative, it will take a lot of time and energy. This does not serve the purpose of saving time and effort. Therefore, the number of students selected for the survey must be appropriate.

Statistical survey PPT, part 2: summary

Comprehensive survey and sampling survey are two ways to collect data. Comprehensive survey collects comprehensive and accurate data, but it generally costs a lot and takes a long time, and some surveys are not suitable for comprehensive survey. Sampling survey has the characteristics of low cost and time saving. , but whether the sample drawn is representative is directly related to the accuracy of the overall estimate.

Please work as a group to solve the following questions.

Question 3 Compare the average weight of classmates from three grades in your school:

(1) Develop an investigation plan and use your spare time to conduct the investigation;

(2) Based on the collected data, analyze the average weight of students in each grade, and use a line chart to show the changing trend of the average weight as the grade increases;

(3) Arrange a representative from each group to introduce the group's completion of the above problems to the whole class, and make comparisons and comments.

Statistical survey PPT, part 3: in-class exercises

In order to understand the average height of the students in the school, Xiao Ming surveyed the three students sitting next to him and used the average of their heights as an estimate of the average height of the students in the school.

(1) Is Xiao Ming’s survey a sampling survey?

(2) Can this survey result better reflect the overall situation? If not, please explain the reason.

Solution (1) Xiao Ming’s survey is a sampling survey.

(2) This survey result cannot better reflect the overall situation. Because the whole school

Students are of different age groups and have large height differences. The sample selected by Xiao Ming is not representative.

A certain class will choose 3 students to represent the class in inter-class exchange activities. Now choose according to the following method: write the names of all the students in the class on small pieces of paper with no obvious difference, and mix the pieces of paper in a box , after stirring thoroughly, randomly select 3 pieces of paper and select 3 students according to the names written on the pieces of paper. Do you think the above extraction process is simple random sampling? Why?

Solution: The above extraction process is simple random sampling. Because every student has an equal chance of being selected.

Among the following surveys, which ones are suitable for comprehensive surveys and which ones are suitable for sample surveys?

(1) Investigate the impact resistance of a certain batch of cars;

(2) Understand the height of students in a certain class;

(3) Investigate the ratings of the Spring Festival Gala;

(4) Select the fastest sprinter from a certain school to participate in the city-wide competition.

Solution (2)(4) is suitable for comprehensive survey, and (1)(3) is suitable for sampling survey.

Statistical Survey PPT, Part 4: Expanding Applications

During the 1936 U.S. presidential election, Literary Digest magazine mailed questionnaires to 10 million voters, whose lists were selected from phone books, club rosters, and magazine subscribers. As a result, approximately 2.4 million voters returned the survey. Based on the answers of these voters, the magazine predicted that Republican Langdon would be elected. But the election results were completely beyond their expectations. Democratic Roosevelt was elected with a majority of votes. This major mistake caused this magazine, which is very prestigious in polling, to lose face. So why did the magazine predict failure?

It turns out that the 1930s was a period of economic recession in the United States. At that time, most Americans who could install telephones, join upper-class clubs, or subscribe to magazines were wealthy and supported the Republican Party. In other words, although the sample size selected by this magazine was huge, But the sample is not representative.

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Update Time: 2024-11-09

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