"Frequency and Frequency" Data Collection and Processing PPT Courseware 3

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"Frequency and Frequency" Data Collection and Processing PPT Courseware 3

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Answer the following questions first, then fill in the form below:

(1) In these 10 trials, how often does "tails face up" occur?

What is the relationship between the frequency of "heads" and the frequency of "tails"?

The sum of the frequency of "heads" is 4 and the frequency of "tails" is 6 is 10, which is equal to the total number of coin tosses.

(2) In these 10 coin tosses, how often does it land "tails"?

What is the relationship between the frequency of "heads" and the frequency of "tails"?

The sum of the frequency of "heads" is 0.4 and the frequency of "tails" is 0.6 is equal to 1.

How to compare Xiaofang's first 15 shots and the last 25 shots?

(1) Observe the changes in the frequency of various scores between the first 15 shots and the last 25 shots?

Answer: Compared with the first 15 times, the frequency of low scores in the last 25 times has decreased, while the frequency of high scores has increased.

(2) In the first 15 shots, there were 5 scores of 8 points. Its proportion to the total number of shots (15 shots) is 5/15=1/3, so the frequency is the weight. Calculate the score of the first 15 shots Weighted average vs. weighted average of scores from the last 25 shots. How does the weighted average of observed scores change?

Answer: The average score in the first 15 times: 7.87, the average score in the last 25 times: 8.72, and the weighted average increases.

(3) What do these observed changes indicate?

Answer: The frequency of high scores in the last 25 times increases, indicating that the accuracy of shooting has improved and the number of high scores has increased, thus causing the average score to increase.

practise

1. Given a set of data as follows:

14, 14, 14, 16, 16, 17, 17,

17, 20, 20, 20, 20, 20, 25.

(1) Write the frequency and frequency of each number appearing in the array;

(2) Use the weighted average method to calculate the average of this set of data.

Explore

How did Xiaojun solve Grandma Li's difficulties?

(1) Start with investigation and data collection.

Xiaojun went to Grandma Li's convenience store to investigate and found that the milk and beverages sold by Grandma Li mainly include five varieties: A, B, C, D, and E. In order to understand the sales of each variety, Xiaojun made statistics for two consecutive weeks. The sales volume of each variety on each day. The following table is the results of Xiao Ming’s statistics:

(2) Statistics of sales of each variety.

Based on the collected information, count the weekly sales of each variety and fill in the following statistical table:

(3) Analyze statistical results.

Think about it: What insights can you get from the statistics above?

(4) Determine the business plan.

Various milk products and beverages should be stocked in proportion to the sales volume of each variety, but sales volume fluctuates from time to time. In order to reduce the impact of sales fluctuations, Xiaojun calculated the average sales volume of each variety every week, as shown in the table below .

Example 1 In order to understand the physical fitness of ninth-grade students, a school randomly checked 30 of them, tested the number of sit-ups in 1 minute, and drew a frequency distribution histogram as shown in Figure 7.1-1. Please follow According to the calculation shown in the figure, the frequency of sit-ups between 15 and 20 times is ( ).

A.0.1 B.0.17 C.0.33 D.0.4

From the meaning of the question: there are 30-(12+10+5)=3 people who can do sit-ups between 15 and 20 times, so the frequency is 3/30=0.1. Therefore, choose A.

Example 2 Which of the following statements is correct ( ).

A. The probability of winning a game is 1/10. If you play this game 10 times, you will definitely win.

B. In order to understand the mental health situation of middle school students across the country, a census should be used.

C. The mode and median of a set of data 6, 8, 7, 8, 8, 9, and 10 are both 8.

D. If the variance of group A data is S A2 = 0.01 and the variance of group B data is S B2 = 0.1, then group B data is more stable than group A data.

∵ The winning probability of the game is 1/10, which does not mean that you will definitely win if you play this game 10 times, excluding A; In order to understand the mental health situation of middle school students across the country, a sample survey should be used, excluding B; ∵ The variance of a set of data The smaller it is, the more stable this set of data is. ∴ excludes D, so C is selected.

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Update Time: 2024-09-09

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