(20 13, Zigong, Sichuan, 10) In order to help our city build a provincial-level civilized city, a proofreader made statistics on the number of volunteers in each class in 8th grade.

Solution: (1)∵ There are 4 classes and 6 volunteers. ∴ The total number of classes is: 4 ∴ 20% = 20 (each).

There are two volunteer classes: 20-4-5-4-3-2 = 2 (each)

The average number of civilized behavior persuasion volunteers in this grade is: (4× 6+5× 5+4+3× 3+2× 2+2×1) ÷ 20 = 4 (name).

Complete the bar chart as follows:

(2) From (1), there are only two volunteers in two classes to persuade civilized behavior, and there are ***4 students. Let A 1, A 2 for one class, B 1, and B 2 for one class. Draw a tree diagram:

As can be seen from the tree diagram, * * has 12 possible situations, and the possibility of each result is equal, among which * * * from a class has 4 situations.

∴ The probability that the selected two civilized behaviors persuade volunteers to come from the same class is:

(1) According to the calculation of 20% of six volunteer classes, the total number of classes can be obtained, then the number of two volunteer classes can be obtained, and then the average number of volunteers in each class can be obtained.

(2) According to (1), there are two classes with only two volunteers and four students. Let A 1, A 2 come from a class, B 1, and B 2 come from a class. The tree diagram or list shows that there are four situations of * * * from a class, so the two volunteers are from the same class.