Calligraphy group: 22=40=62 (person)
Computer group: 50+32=82 (person)
Science and Technology Group: 25+45=70 (person)
Answer: The computer interest group has the largest number and the art interest group has the smallest number.
(2) Middle-grade students have the largest number of computer interest groups, so middle-grade students like to join computer interest groups best;
Senior students participate in science and technology groups with the largest number, so senior students like to participate in science and technology interest groups best;
(3) Draw a histogram according to the data in the statistical table as follows: