(1) According to the meaning of the question: 2÷20%= 10 (pieces), that is, the math interest group counted 10 time periods;

B has 10×30%=3 (pieces), and D has 10-(4+3+2)= 1 (pieces) to complete the bar chart, as shown in the figure:

So the answer is:10;

(2) According to the meaning of the question: 110× (3×1+2×1× 3) =1(people), that is, there are1people jaywalking in every time period;

So the answer is:1;

(3) The list is as follows: (where 1 stands for students)? 1 2 3 4 1-(2, 1) (3, 1) (4, 1)2 (1, 2)-(3,2) (4,2

Then p = 6 12 = 12.