Eight people participated in calligraphy.

(1) Complete the statistical table according to the information given in the question, and draw the histogram according to the analysis as follows:

(2) According to the length of the bar in the bar statistics, it can be seen that the math group has the largest number of people and the art group has the least number;

So, the answer is: math, art.

(3) Ask a question: How many students in Grade Four joined the interest group?